Butter two tall, straight-sided cake pans. I used 8 inch pans, but you could use 9 inch or even a square or rectangular pan… just make sure it has high sides!
Once your pans are buttered, dust with flour. Be sure to remove the excess flour!
In your mixer, cream the butter and sugar until light and fluffy. I creamed the butter alone until very smooth before adding the sugar, then beat on med-high for another 5 minutes.
Add in the eggs, one at a time, mixing well until each is incorporated.
Add the vanilla extract to the milk.
Alternating between the dry ingredients and the wet ones, add to the butter and sugar. Mix until combined after each addition. Beginning and ending with the dry mix works best!
Using a spatula (not your mixer), gently fold in the egg whites. Stop when the egg whites are combined, but not completely incorporated.
Pour the batter evenly into your pans. Bang the cake firmly on the counter (keep pan flat) to make sure there are no air pockets.
Bake for 40 to 45 minutes or until a toothpick cake comes out clean.
Place butter in mixer and whip until smooth.
Slowly add sugar - about a half cup at a time. Scrap down the sides often. Mix until all is well combined.
Slowly add milk.
Add vanilla and salt.
Make sure that cakes are cool before icing.** You can make this cake in a 9x13 pan as well. Just grease it first, no flouring needed. Bake at 350° for 35-40 minutes, or until it passes the toothpick test. *** If you are baking in a 9x13 pan, cut the frosting recipe to 2 sticks of butter, half a pound of sugar, and a splash of milk and vanilla to consistency. This is because you won't have the double layer, so half the icing is plenty!