- Unsalted butter, for pans
- 1 1/2 cups unsweetened cocoa powder, plus more for pans
- 3 cups all-purpose flour
- 3 cups sugar
- 1 tablespoon baking soda
- 1 1/2 teaspoons baking powder
- 1 1/2 teaspoons salt
- 3 large eggs
- 1 1/2 cups buttermilk
- 3/4 cup vegetable oil
- 1 1/2 teaspoons pure vanilla extract
- Preheat oven to 350 degrees. Butter round or square cake pans, and line bottoms with parchment; butter parchment, and dust with cocoa.
- Into the bowl of an electric mixer fitted with the paddle attachment, sift cocoa, flour, sugar, baking soda, baking powder, and salt. With the mixer on low, stir in eggs, 1 1/2 cups warm water, buttermilk, vegetable oil, and vanilla until smooth, about 3 minutes.
- Divide batter among prepared pans. Bake, rotating once, until tester inserted in center comes out clean, 35 to 45 minutes for 8-inch layers, depending on amount of batter.
- Let cakes cool in pans on a wire rack for 20 minutes, then remove from pans and cool completely, right side up on rack.
Cake can be made in advance and stored up to 1 day in refrigerator.