This Sourdough Discard Funfetti Cake is everything you loved about the boxed version, grown all the way up. Three tender 8-inch layers bake up with a tight, bouncy crumb thanks to whipped egg whites, a whisper of tang from sourdough discard, and a confetti of rainbow jimmies in every slice. It's frosted in a light, almost cloud-like whipped vanilla buttercream that makes the whole thing feel like a celebration before you've even cut into it.
If you love putting your starter to work in sweets, this slots right in next to my fudgy sourdough discard brownies and sourdough discard coffee cake — and if you're after another showstopping layer cake, the lemon blueberry mascarpone cake and lemon blackberry cake are my go-tos for spring.
Quick Look: Sourdough Funfetti Cake
⏱️ Ready In: about 2 hours 30 minutes (including cooling)
🔥 Bake Time: 22–26 minutes
🍽️ Serves: 12–16
✨ Calories: 744 per slice (for 12 generous slices)
🥄 Main Ingredients: sourdough discard, AP flour, egg whites, butter, rainbow jimmies
🌿 Dietary: Vegetarian
💛 Why You'll Love It: nostalgic funfetti flavor with a bakery-tender crumb and a smart way to use up discard
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Why you'll love this recipe
- Its tight, bouncy crumb. Whipping the egg whites separately and folding them in gives this cake a springy, almost cottony texture you just can't get from a dump-and-stir batter.
- A genuinely good use for discard. Like my sourdough discard peanut butter cookies and sourdough snickerdoodle cookies, this recipe turns the starter you'd otherwise toss into something worth celebrating — and the subtle tang keeps the sweetness in check.
- Real, nostalgic funfetti flavor. A little almond extract is the not-so-secret ingredient that makes it taste like the boxed mix you grew up on, only better.
- A frosting that feels like a cloud. The whipped vanilla buttercream is light and silky rather than dense and toothache-sweet — the same one I reach for on sourdough chocolate cupcakes.
- Built for celebrations. It's a true layer cake, so it's perfect for birthdays alongside something fun like strawberry crunch cupcakes on the dessert table.
Jump to:
- Quick Look: Sourdough Funfetti Cake
- Why you'll love this recipe
- Ingredients You'll Need
- Easy Substitutions & Variations
- How to Make Sourdough Funfetti Cake
- Expert Tips
- What Makes This Recipe Special?
- Sourdough Discard Funfetti Cake FAQs
- Sourdough Funfetti Cake Troubleshooting Guide
- Storage
- Other Cake Recipes to Consider
- Sourdough Funfetti Layer Cake
Ingredients You'll Need
- Baking powder and baking soda — your lift; the discard's slight acidity gives the soda something to react with.
- Nutmeg — gives the vanilla buttercream a little personality.
- Neutral oil — keeps the crumb moist and soft for days.
- Sourdough discard — room temperature; adds subtle tang and a little extra tenderness.
- Whole milk and sour cream — both at room temperature for a smooth, rich batter.
- Egg whites and cream of tartar — whipped to soft-medium peaks for that signature bouncy crumb.
- Rainbow jimmies — the classic confetti; jimmies bleed less than nonpareils.
- Unsalted butter — room temperature, whipped long enough to go pale and fluffy.
See recipe card for quantities.
Easy Substitutions & Variations
- No sourdough discard? Replace the 75 g of discard with 75 g of a 1:1 flour-and-water mix (about 38 g AP flour whisked with 37 g water), plus 1 teaspoon of lemon juice or white vinegar to mimic the tang that activates the baking soda. You'll lose the faint sourdough character, but the crumb stays just as tender.
- No sour cream? Full-fat plain Greek yogurt works as a one-to-one swap and keeps the same richness.
- Dairy-free: Use a plain unsweetened oat or soy milk, a dairy-free sour cream, and a vegan stick butter for the frosting. The crumb stays tender, much like in my oat milk pancakes.
- Skip the almond extract if you have an allergy or just aren't a fan — bump the vanilla up by ½ teaspoon to make up for it.
- Make it a sheet cake by baking the batter in a 9x13 pan for 30–38 minutes, the way I do for my sourdough chocolate sheet cake with brown butter buttercream.
- Cupcakes: This batter makes about 24 cupcakes; bake at 350°F for 17–20 minutes.
How to Make Sourdough Funfetti Cake
Note: I bake by weight for accuracy. Cup measurements are approximate and may vary depending on how you scoop.
Step 1: Prep your pans and mix the batter base. Preheat the oven to 350°F (175°C). Grease three 8-inch cake pans, line the bottoms with parchment, and grease again — having all three ready matters, because once the whites go in you want the batter in the oven without delay. In a large bowl, whisk together the AP flour, baking powder, baking soda, and salt.
In a separate bowl or large measuring jug, whisk the neutral oil, granulated sugar, sourdough discard, whole milk, sour cream, vanilla, and almond extract until smooth — the discard will look streaky at first, so keep whisking until it's fully incorporated.
Step 2: Combine wet and dry. Pour the wet ingredients into the dry and whisk gently until just combined and no dry streaks remain. Don't overmix — the batter will be fairly fluid. Set aside.
Step 3: Whip the whites, then fold them in with the sprinkles. In a completely clean, grease-free bowl, beat the egg whites and cream of tartar on medium until foamy, then increase to medium-high and whip to soft-to-medium peaks — a gentle drooping peak, not stiff or dry (3–4 minutes). Whisk about one-third of the whites firmly into the batter to loosen it, then fold in the rest in two additions with a wide spatula, using long strokes from the bottom up and over. Once only a few streaks remain, scatter the rainbow jimmies over the batter and fold with just 3–4 more strokes. Work quickly and don't deflate.
Step 4: Divide, bake, and cool. Divide the batter evenly among the three prepared pans — a kitchen scale makes this easy (weigh the total and divide by three). Bake for 22–26 minutes, until the tops are set, spring back when lightly touched, and a toothpick comes out with just a few moist crumbs. Cool in the pans for 10 minutes, then turn out onto a wire rack and cool completely. Do not frost until fully cool — the whipped buttercream will melt on a warm cake.
Step 5: Make the buttercream. Beat the unsalted butter on medium-high for 4–5 minutes until very pale and fluffy — this is the foundation of the whipped texture, so don't rush it. Add the powdered sugar in three additions on low, then the vanilla and a pinch of salt. With the mixer on medium-high, stream in the cold heavy cream slowly and whip for another 3–4 minutes, until the buttercream is noticeably lighter, silkier, and almost cloud-like. It should hold peaks but feel airy rather than dense.
Step 6: Decorate. Level your cake layers if needed. Stack with a generous layer of buttercream between each. Apply a thin crumb coat, chill for 15 minutes, then apply the final coat. Decorate with rainbow jimmies, candles, and whatever your heart desires.
Weigh your ingredients! Using a kitchen scale ensures your measurements are accurate, which is key for getting consistent results in baking. It takes the guesswork out of measuring and helps your recipes turn out exactly as intended every time.
Expert Tips
- Bring everything to room temperature. Room-temp discard, milk, sour cream, and egg whites all combine more smoothly — and room-temp whites whip faster and to more volume than cold ones.
- Start with a spotless bowl. Even a trace of yolk or grease will keep your whites from whipping. Wipe the bowl with a paper towel and a splash of white vinegar if you're unsure.
- Don't overwhip the whites. Soft-to-medium peaks fold in cleanly. Stiff, dry whites break into clumps and leave white streaks in the batter.
- Fold, don't stir. Once the whites go in, switch to a wide spatula and long, gentle strokes. Overmixing here deflates the air you just worked to build.
- Weigh your batter. Dividing by weight gives you three even layers that bake in the same amount of time — no guessing, no domed-then-flat mismatch.
- Whip the butter long enough. Those 4–5 minutes of beating the butter before any sugar goes in are what make the frosting light. Pale and fluffy is the goal.
What Makes This Recipe Special?
Most funfetti cakes are a one-bowl affair, and they're fine — but they bake up a little dense and tight in a way that reads more "muffin" than "celebration cake." Whipping the egg whites separately and folding them in is the difference-maker: it traps air directly in the batter, so the crumb springs back when you press it and feels almost weightless on the fork.
The sourdough discard does quiet, double duty. Its acidity activates the baking soda for extra lift, and it lends a barely-there tang that keeps an otherwise very sweet cake from tipping over the edge. Pair that with the whipped vanilla buttercream — light enough that you'll happily go back for a second slice — and you've got a funfetti cake that tastes like childhood but eats like a bakery.
Sourdough Discard Funfetti Cake FAQs
Not really. At this ratio the discard reads as a faint tang in the background, not a sour, bready flavor. It mostly just makes the crumb more tender.
Rainbow jimmies (the little cylinders) are best. They hold their shape and color far better than nonpareils (the tiny balls), which bleed quickly and can turn the batter gray.
No, but it's what gives Funfetti that nostalgic boxed-mix flavor. It's subtle at ½ teaspoon. If you skip it, add an extra ½ teaspoon of vanilla.
Yes — divide the batter between two pans and bake a few minutes longer, watching for the toothpick test. The layers will be taller, so check at 28–32 minutes.
You can, though discard is ideal here since it's not contributing to rise. If using fed, active starter, expect a slightly puffier batter; the result will still work.
Sourdough Funfetti Cake Troubleshooting Guide
| Problem | Cause | Fix |
|---|---|---|
| Dense, gummy crumb | Whites overfolded or deflated | Fold just until no streaks remain; get the batter into the oven quickly |
| White streaks in baked cake | Whites underfolded or whipped too stiff | Whip only to soft-medium peaks; fold a little more thoroughly |
| Sprinkles bled into gray streaks | Used nonpareils, or folded too long | Use jimmies and fold them in with only 3–4 strokes |
| Layers domed or uneven | Batter not divided evenly | Weigh the batter and split it equally across pans |
| Frosting soupy or sliding | Cake still warm, or butter too soft | Cool layers completely; chill frosting briefly and re-whip |
| Frosting dense, not fluffy | Butter not whipped long enough | Beat butter 4–5 minutes before adding sugar; whip again after the cream |
Storage
- Room temperature: A frosted cake keeps, loosely covered, for up to 2 days in a cool spot.
- Refrigerator: Store in an airtight container for up to 5 days. Let slices sit at room temperature for 20–30 minutes before serving so the buttercream softens.
- Freezer: Baked, unfrosted layers wrap tightly in plastic and freeze beautifully for up to a month — thaw at room temperature before frosting. The buttercream keeps refrigerated for 1 week; bring it back to room temp and re-whip before using.
Other Cake Recipes to Consider
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Sourdough Funfetti Layer Cake
Equipment
- Three 8-inch round cake pans
- Stand mixer or hand mixer
- Kitchen Scale
- Wide spatula
- Wire cooling rack
- Offset spatula (for frosting)
Ingredients
For the cake:
- 360 g 3 cups AP flour
- 2½ teaspoon baking powder
- ½ teaspoon baking soda
- ¾ teaspoon 0.8 teaspoon salt
- 120 ml ½ cup neutral oil (vegetable or canola)
- 275 g 1⅜ cups granulated sugar
- 75 g sourdough discard room temperature
- 240 ml 1 cup whole milk, room temperature
- 120 g ½ cup sour cream, room temperature
- 2½ teaspoon vanilla extract
- ½ teaspoon almond extract optional but recommended
- 5 egg whites room temperature
- ¼ teaspoon cream of tartar
- 80 g rainbow jimmies
For the whipped vanilla buttercream:
- 340 g 1½ cups unsalted butter, room temperature
- 480 g 4 cups powdered sugar, sifted
- 60 ml ¼ cup heavy cream, cold
- 2 teaspoon vanilla extract
- 1 pinch salt
- 1 pinch nutmeg optional
- 30 g rainbow jimmies for decorating
Instructions
- Prep: Preheat oven to 350°F (175°C). Grease three 8-inch cake pans and line the bottoms with parchment.
- Dry ingredients: Whisk together the flour, baking powder, baking soda, and salt in a large bowl. Set aside.360 g 3 cups AP flour, 2½ teaspoon baking powder, ½ teaspoon baking soda, ¾ teaspoon 0.8 teaspoon salt
- Wet ingredients: In a separate bowl, whisk together the oil, sugar, sourdough discard, milk, sour cream, vanilla, and almond extract until smooth. Keep whisking until the discard is fully incorporated.120 ml ½ cup neutral oil (vegetable or canola), 275 g 1⅜ cups granulated sugar, 75 g sourdough discard, 240 ml 1 cup whole milk, room temperature, 120 g ½ cup sour cream, room temperature, 2½ teaspoon vanilla extract, ½ teaspoon almond extract
- Combine: Pour the wet into the dry and whisk gently until just combined and no dry streaks remain. Don't overmix; the batter will be fairly fluid.
- Whip whites: In a clean, grease-free bowl, beat the egg whites and cream of tartar on medium until foamy, then medium-high to soft-medium peaks (3–4 minutes).5 egg whites, ¼ teaspoon cream of tartar
- Fold: Whisk one-third of the whites into the batter to loosen it, then fold in the rest in two additions with a wide spatula until no streaks remain. Work quickly.
- Sprinkles: Scatter the rainbow jimmies over the batter and fold in with just 3–4 strokes.80 g rainbow jimmies
- Bake: Divide the batter evenly among the pans (weigh for accuracy). Bake 22–26 minutes, until the tops spring back and a toothpick comes out with a few moist crumbs.
- Cool: Cool in pans 10 minutes, then turn out onto a wire rack and cool completely before frosting.
- Buttercream: Beat the butter on medium-high 4–5 minutes until pale and fluffy. Add powdered sugar in three additions on low. Add vanilla, pinch of nutmeg, and salt. Stream in the cold cream on medium-high and whip 3–4 minutes until light and cloud-like.340 g 1½ cups unsalted butter, room temperature, 480 g 4 cups powdered sugar, sifted, 2 teaspoon vanilla extract, 1 pinch salt, 1 pinch nutmeg , 60 ml ¼ cup heavy cream, cold
- Assemble: Level the layers if needed. Stack with buttercream between each, apply a thin crumb coat, chill 15 minutes, then apply the final coat and decorate with rainbow jimmies.30 g rainbow jimmies
Notes
- Egg white tips: Room-temp whites whip faster and fuller than cold. Any trace of yolk or grease will prevent proper whipping — wipe the bowl with a paper towel and a splash of white vinegar if unsure.
- Discard hydration: Written for 100% hydration discard (equal parts flour and water). Thicker discard makes a slightly stiffer batter, which is fine.
- Sprinkle bleeding: Jimmies bleed less than nonpareils but still tint the batter over time. Fold them in last and get the batter in the oven fast.
- Almond extract: The secret to that nostalgic boxed-funfetti flavor. Subtle at ½ teaspoon but worth including.
- Make-ahead: Baked layers wrap and freeze for up to a month. Buttercream keeps refrigerated for 1 week — re-whip before using.
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