1 cup buttermilk
1⁄2 cup whole milk
9 large egg whites, lightly beaten
1 tablespoon vanilla
1 vanilla bean, scraped
4 1⁄2 cups cake flour (not self-rising)
2 teaspoons baking powder
2 sticks butter, room temperature
1 1⁄2 teaspoons salt
2 1⁄4 cups sugar
Preheat oven to 350.
Butter and flour two 9- inch round cake pans, tapping out excess flour; set aside.
In a medium bowl, combine the buttermilk, milk, egg whites, and vanilla extract and beans; set aside. In another bowl, whisk the flour, baking powder, and salt; set aside.
In an electric mixer, beat the butter until fluffy. Add the sugar and beat until combined, about 2 minutes.
Working in several batches, alternately add the flour mixture and milk mixture, ending with milk mixture. Beat after each addition until the mixture is just combined.
Place mixture in tin and bake for 35 to 40 minutes, until the cake is beginning to brown around the edges and a tester comes out clean.
Let cake cool in pan on a rack for about 5 minutes. Remove the cake from their pan and allow to cool completely.
If the cake is domed, slice off the domed portion to create a flat cake.
For the icing l just made a large batch of my regular butter icing
2 cups of icing sugar
1/4 tsp vanilla bean
mix all ingredients until light and fluffy.