3/4cupegg whites plus 3 tablespoons*(This is about 6-7 large egg whites)
Using a stand mixer, beat the egg whites with the whisk attachment until they are stiff and form peaks. This may take a minute or two. Pour the egg whites into another bowl and place them in the refrigerator until you're ready to add them to the batter.
Using the same bowl that you used to beat the egg whites, place the softened butter in and cream the butter for about 2 minutes (using the beater blade attachmenuntil it is white in appearance.
Add the sugar to the butter and beat with the paddle attachment until fluffy (about another 1-2 minutes).
In a medium bowl, whisk together the dry ingredients: flour (measured carefully*), salt and baking powder. Set aside.
In another bowl, combine the milk and vanilla extract.
Add the flour mixture to the butter mixture alternately with the milk.
Add the stiffly beaten eggs to the cake batter. Fold the egg whites in gently. Do not overmix at this point. If you do, your cake will become more dense.
Grease and flour 2 9" round cake pans. Line with parchment paper to ensure the cakes come out cleanly. Pour the cake batter equally into the prepared cake pans.
Bake the cakes at 350ºF for 25-27 minutes or until the top bounces back when you touch it.
Allow the cakes to cool for 10 minutes, then loosen the edges and remove them from the pans to a cooling rack, allowing them to cool completely.
Frost the cakes once they are cooled. If you are not frosting the cakes right away, wrap them in plastic wrap so that they stay fresh.
*Frost with your favorite vanilla buttercream. **The calories shown are based on the cake being cut into 15 pieces, with 1 serving being 1 slice of unfrosted cake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate.