A good recipe for moist white cake is Mrs. Billett's White Cake from MyRecipes.com. The recipe calls for butter, sugar, cake flour, egg whites, milk, three round cake pans and parchment paper.
Grease the cake pans and the parchment after pressing the paper to the bottom of the pans, and then dust the parchment with flour. Combine 1 cup of milk and 1 1/2 teaspoons of vanilla extract in a bowl. In another bowl, cream 1 cup of softened butter, and add in 2 cups of sugar. In a third bowl, sift 3 cups of cake flour with 1 tablespoon of baking powder. In the last bowl, beat 5 egg whites until they form stiff peaks.
Alternately mix the flour mixture and the milk mixture into the butter mixture, and then fold in the beaten egg whites. Spoon the batter into the three pans, and bake them at 350 degrees F for 20 to 23 minutes. Meanwhile, combine 1 cup of softened butter and 1/4 teaspoon of salt for the buttercream frosting. Alternately stir in 1 32-ounce package of powdered sugar and 6 tablespoons of milk, and mix in 1 tablespoon of vanilla extract. Allow the cakes to cool completely before assembling them with the buttercream frosting between the layers.