Prep pans: Start by preheating your oven to 350 degrees F. Line the bottom of two 9-inch round cake pans with parchment paper and lightly spray the insides with nonstick cooking spray. This ensures your cake comes out perfectly!
Combine dry ingredients: In a mixing bowl, sift together all-purpose flour, cake flour, baking powder, baking soda, and salt. This step adds air, ensuring a light texture.
Mix wet ingredients: In a separate bowl, beat together butter, sugar, and lemon zest using an electric mixer until the mixture becomes pale and fluffy, about 3 to 4 minutes. This is the foundation of your cake's flavor.
Add eggs: Add whole eggs to the butter mixture, mixing well. Then, incorporate the egg whites one at a time, ensuring each is fully mixed before adding the next. This technique traps air for a lighter cake.
Incorporate dry and wet: Gradually mix in the dry ingredients and buttermilk, alternating between them. Stir gently to combine. You want the batter to be smooth but don’t overmix!
Divide the batter: Evenly distribute the batter between your two prepared pans. This ensures that both cakes bake uniformly.
Bake the cakes: Place the pans in your preheated oven and bake for 24 to 29 minutes, or until a toothpick inserted in the center comes out clean. The cakes should be a lovely golden brown.
Cool the cakes: Once baked, allow the cakes to cool for several minutes in the pans. Then, carefully transfer them to a wire rack to cool completely.
Make the frosting: In a mixing bowl, add butter and beat for 1 minute. Then, mix in powdered sugar, half of the lemon juice, and lemon zest. Beat until smooth and creamy, about 3 minutes. Adjust consistency with more sugar or juice if needed.
Frost the cake: Once the cakes are completely cool, generously frost the top of one layer before placing the other on top and frosting the entire cake. Allow it to set for a moment before serving.
