Cafe Vanilla Cupcake

9 eggs, separated
3/4 lb unsalted butter
3 cups sugar
1 1/2 teaspoons vanilla
3 cups pastry flour (can substitute 2/3 all-purpose flour and 1/3 cake flour)
1 1/2 teaspoons baking powder
3/4 teaspoon baking soda
1/2 teaspoon salt
1 1/2 cups buttermilk

Butter or spray two 8 or 9 inch cake pans and line the bottom with parchment. Preheat the oven to 350.
Cream butter and sugar together; beat in yolks; add vanilla and set aside.
Sift dry ingredients together.
Beat egg whites to soft peaks.
Mix dry ingredients and buttermilk alternately (in three increments starting with the dry ingredients) into the egg/butter mixture - do not overbeat.
Fold in the egg whites.
Fill pans about 2/3 full and bake for about 35-40 minutes until a tester comes out clean - cakes should feel slightly springy when pressed in the middle.