Fresh lemon juice from 1 lemon(about 3 ½ tablespoons)
1teaspoonpure vanilla extract
Assembly
3/4cupvanilla cookie crumbs
Powdered sugarfor dusting
Instructions
PREPARE OVEN: Preheat the oven to 350°F. Grease and flour a deep 8-inch round cake pan.
MIX DRY INGREDIENTS: In a medium bowl, sift together 1 cup all-purpose flour, 1 teaspoon baking powder, and ¼ teaspoon kosher salt. Set aside.
WHIP EGGS: In a large mixing bowl, add 4 large eggs. Beat on medium speed for 1 minute. Gradually add 1 cup granulated sugar and ½ teaspoon pure vanilla extract. Continue beating for 7 to 8 minutes, until the mixture is thick, pale, and holds ribbons.
FOLD BATTER: Gently fold the dry ingredients into the egg mixture in three additions, alternating with ¼ cup melted butter and ¼ cup whole milk, starting and ending with the dry ingredients. Fold carefully to avoid deflating the batter.
BAKE: Pour the batter into the prepared pan and smooth the top. Bake for 30 to 35 minutes, until a toothpick inserted into the center comes out clean.
COOL CAKE: Let the cake cool in the pan for 10 minutes. Turn out onto a wire rack and cool completely.
WHIP CREAM: In a clean mixing bowl, whip 1 cup heavy whipping cream until stiff peaks form. Set aside.
MAKE FILLING: In another bowl, add 8 ounces mascarpone cheese, 1 cup powdered sugar, lemon zest, lemon juice, and 1 teaspoon pure vanilla extract. Beat until smooth and creamy.
COMBINE: Gently fold the whipped cream into the mascarpone mixture until fully combined. Reserve ½ cup of the lemon cream for the exterior of the cake.
SLICE CAKE: Once completely cooled, use a long serrated knife to slice the cake horizontally into two even layers.
ASSEMBLE: Place the bottom layer on a serving plate. Spread the lemon cream filling evenly over the top, leaving the reserved portion aside. Place the second layer on top.
COAT SIDES: Spread the reserved ½ cup lemon cream around the sides of the cake. Gently press the vanilla cookie crumbs into the sides to coat.
CHILL: Refrigerate the cake for at least 2 hours to set.
FINISH: Just before serving, dust the top lightly with powdered sugar.
Notes
Make-Ahead: This cake can be assembled up to 24 hours ahead. Keep refrigerated until ready to serve.Storage: Store covered in the refrigerator for up to 3 days.Freezing: Freeze the unfrosted sponge cake tightly wrapped for up to 2 months. Thaw completely before filling and assembling.Technique Tip: Be sure to beat the eggs and sugar for the full 7 to 8 minutes. This step builds the structure of the sponge cake. If the batter sits too long before baking, gently re-whip for 30 seconds to restore volume.