Preheat oven to 350 degrees. Make the cake: Butter
three 9-inch round cake pans, and dust with flour,
tapping out excess. Sift flour, granulated sugar, cocoa,
baking soda, baking powder, and 1 1/2 teaspoons coarse
salt into the bowl of a mixer. Beat on low speed until
just combined. Raise speed to medium, and add eggs,
buttermilk, 1 1/2 cups warm water, oil, and vanilla.
Beat until smooth, about 3 minutes.