Sourdough Funfetti Layer Cake
A three-layer 8-inch funfetti cake with a tight, bouncy crumb from whipped egg whites and subtle tang from sourdough discard, frosted with a light whipped vanilla buttercream.
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.
Nutrition
Calories: 744kcalCarbohydrates: 98gProtein: 6gFat: 38gSaturated Fat: 19gPolyunsaturated Fat: 6gMonounsaturated Fat: 9gTrans Fat: 1gCholesterol: 75mgSodium: 321mgPotassium: 122mgFiber: 1gSugar: 72gVitamin A: 878IUVitamin C: 0.1mgCalcium: 101mgIron: 2mg
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