Preheat the oven to 325 degrees F. Spray three 8-inch round cake pans with nonstick spray. Line the bottom of each pan with parchment paper, then spray the parchment paper. Set aside.
In a medium size mixing bowl, whisk together the flour, sugar, cocoa, baking soda, baking powder, and salt. Set aside.
In another bowl, combine the buttermilk, oil, eggs, water (or coffee) and vanilla. Whisk until combined.
With the mixer on low speed, slowly add the wet ingredients to the dry, scraping the bottom of the bowl with a rubber spatula.
Evenly divide the batter into each of the three pans (about 15 to 16 ounces of batter in each 8-inch pan). Bake for 23 to 28 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs on it.
Cool in the pans for 10 minutes, then turn them out onto a cooling rack and cool completely. (I like to spray my cooling racks with nonstick spray to ensure non of the cake sticks to the racks).
If needed, level your cake layers to ensure a completely even surface for frosting and stacking. After leveling you can wrap each cake layer in plastic wrap and freeze until ready to use.