Homemade Lemon Cake Ingredients For the Cake: 5 egg whites, room temperature 3/4 cup buttermilk 2 lemons, zested 3/4 cup unsalted butter, softened 1 3/4 cup granulated sugar 2 1/2 cup cake flour 1 Tbsp baking powder 1/2 tsp kosher salt For the Filling: 4oz unsalted butter 4 oz cream cheese 2 cup powdered sugar