Bake your cake: In the bowl of your mixer, combine sugar, cocoa powder, flour, baking soda, baking powder, and salt. Add eggs, oil, and buttermilk and beat on medium speed for two minutes. Scrape sides of bowl and stir in boiling water. Divide batter into cake pans (batter will be thin) and bake for 30 minutes or until tops spring back when lightly touched. Allow cakes to cool in pans for about 5 minutes, then remove to cooling racks to cool completely.