In a large bowl cream together the butter, sugar, vanilla extract, and egg whites.
In a separate bowl add the cake flour, salt, and baking powder. Sift together.
Start alternatively adding the flour and the buttermilk into the bowl of wet ingredients, while mixing on a low speed.
Once the cake batter is nice and smooth pour the batter into two 9 inch greased and floured cake pans.
Bake the cakes on 350 F, for 25 - 30 minutes or until done.
Remove the cakes from the oven, remove them from the cake pans, and place them on a cooling rack.
Let the cake cool completely before frosting.
( Watch my tutorial on how to do the Rose Swirls)