Heat oven to 350. Prepare two 8-inch round cake pans.
Sift the flour, sugar, cocoa, baking soda, baking powder, and salt into the bowl and mix until combined.
In another bowl, combine the buttermilk, oil, eggs, and vanilla.
With the mixer on low speed, slowly add the wet ingredients to the dry. With mixer still on low, add the coffee and stir just to combine, scraping the bottom of the bowl with a rubber spatula. Pour the batter into the prepared pans (it will be very thin) and bake for 35 to 40 minutes, until a cake tester comes out clean.
Cool in the pans for 30 minutes, then turn them out onto a cooling rack and cool completely