Preheat your oven to 325 degrees F. Spray three 8-inch round cake pans with non-stick spray, line the bottom with parchment paper and spray again. Set aside.
In a medium sized mixing bowl, combine the flour, baking powder and salt. Whisk to combine. Set aside.
In a stand mixer fitted with the paddle attachment, combine the sugar and the butter. Beat on medium-high speed for 2 to 3 minutes, scraping down the sides and the bottom of the bowl half way through.
With the mixer on low speed, alternately add the dry ingredients and the buttermilk, starting and ending with the dry ingredients. Stir in the vanilla.
In a separate bowl, beat the egg whites until stiff peaks form.
Fold the egg whites into the cake batter until no streaks of egg whites are left.
Evenly divide the batter between the three pans, about 15 ounces in each pan. Bake the layers for about 25 to 30 minutes.