Preheat the oven to 350'F. Brush the bottoms and sides of the pans with melted butter and line the
bottoms with parchment paper.
In a large bowl, sift together the cake flour, all-purpose flour, and baking powder. Set aside.
In the bowl of a standing mixer fitted with a paddle attachment, combine the butter and sugar and beat on medium
speed until light and fluffy.
Add the salt and vanilla.
Set the mixer to low speed and gradually add the egg whites, scraping often.
Alternately add the flour mixture and milk to the butter mixture in two batches, starting with the flour mixture.
Scrape down the bowl between each addition and beat until thoroughly combined. Set the mixer to medium-high
speed for about 20 seconds then stop and scrape the sides of the bowl.
Divide the batter evenly between the cake pans or muffin tins. For 9-inch cake pans, bake 1 hour or until a toothpick
comes out clean; for half-sheet pans, bake 45 minutes or until a toothpick comes out clean; for cupcakes, bake 20 to
25 minutes, or until they spring back after being touched.
Allow the cakes to cool for 20 minutes. Once the cake is cool, release it from its pan by running a metal spatula or
knife along the sides of the pan. Flip the cake over onto another pan or cake board and peel away the layer of