Preheat your oven to 350°F (175°C). Grease and flour your two 9-inch round cake pans.
In a medium bowl, whisk together the cake flour, baking powder, and salt. Set aside.
In a separate bowl, combine the buttermilk, egg whites, granulated sugar, lemon zest, and lemon extract. Mix until well combined.
In a large bowl, beat the unsalted butter until creamy and smooth. Gradually add the wet mixture to the creamed butter, mixing until fully incorporated.
Gradually add the dry ingredients to the wet mixture, mixing until just combined. Be careful not to overmix.
Divide the batter evenly between the prepared cake pans. Bake in the preheated oven for 25-30 minutes or until a toothpick inserted in the center comes out clean. Let the cakes cool in the pans for 10 minutes before transferring them to a cooling rack to cool completely.
In a large mixing bowl, beat the unsalted butter for the frosting until soft and creamy. Gradually add the granulated sugar and continue to beat until light and fluffy. Add the egg whites, lemon juice, and vanilla extract, and mix until well combined and smooth.
Once the cake layers are completely cooled, place one layer on a serving platter. Spread a layer of raspberry preserves on top, followed by a layer of lemon buttercream. If desired, add fresh raspberries between the layers. Place the second cake layer on top and repeat the frosting and filling process.
Use the remaining lemon buttercream to frost the top and sides of the cake. Smooth out the frosting with an offset spatula for a clean finish.
Top the cake with fresh raspberries for an extra pop of color and flavor. Slice and serve at your gathering, and enjoy the compliments!
