Prep: Preheat oven to 350°F. Line an 8x8 pan with parchment paper.
Make the shortbread dough: In a large bowl, mix melted butter, granulated sugar, vanilla extract, and salt together. Stir in flour until a soft, crumbly dough forms.
200 grams granulated sugar, 170 grams unsalted butter, ½ teaspoons salt, 1 teaspoons vanilla extract, 240 grams all-purpose flour
Press the crust: Press about ⅔ of the shortbread dough firmly and evenly into the bottom of the prepared pan. Set the remaining ⅓ aside for the crumble topping.
Par-bake the crust: Bake the crust for 12-15 minutes, until just set and very lightly golden at the edges. Remove and let cool for 5 minutes while you make the lemon filling.
Make the lemon filling: In a bowl, whisk together eggs, granulated sugar, fresh lemon juice, lemon zest, flour, and salt until smooth and fully combined. The mixture will be thin and watery — that's normal.
3 large eggs, 200 grams granulated sugar, 120 milliliters fresh lemon juice, 1 tablespoons lemon zest, 30 grams all-purpose flour, ¼ teaspoons salt
Assemble: Pour the lemon filling evenly over the par-baked crust. Crumble the reserved shortbread dough over the top in rough, uneven chunks — don't press it down.
Bake: Bake for 23-27 minutes, until the lemon filling is set at the edges with just a slight jiggle in the center. The top will look like a bunch of small air bubbles popped on the surface, but we will cover that with confectioners' sugar next.
Cool: Let cool completely in the pan — at least 2 hours. The lemon filling needs time to fully set before slicing. Once cool, dust with sifted confectioners sugar. For extra clean cuts, refrigerate for 30-60 minutes before slicing.
confectioners sugar