Preheat oven to 350℉.
Generously grease two 8-inch cake pans, set aside.
Combine dry ingredients in a mixing bowl; flour, baking powder, baking soda, and salt. Set aside.
In the bowl of a stand mixer cream together softened butter and sugar until light and fluffy, about 3-4 minutes.
Add eggs and the egg whites, one at a time until combined with creamed butter mixture.
Add the dry ingredients, a cup at a time, to the wet ingredients until well combined and there are no lumps in the batter.
Add wet ingredients; lemon juice, buttermilk, lemon zest, and vanilla extract. Mix until well combined.
Divide batter evenly between the two greased cake pans.
Bake for 20-25 minutes or until a toothpick inserted in the center of each cake comes out clean.
Remove pans from oven and allow cakes to cool for 15 minutes.
Turn cakes out or there pans and allow them to cool completely on a wire rack.