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 and spray the pans again. Set aside.
Combine the flour, sugar, cocoa, baking soda, baking powder, and salt into the bowl of an electric mixer fitted with a paddle attachment and mix on low speed until combined.
In another bowl, combine the buttermilk, oil, eggs, water, and vanilla.
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 distribute the batter into the prepared pans (about 16 ounces of batter in each pan) and bake for 23 to 27 minutes.
Cool in the pans for 10 to 15 minutes, then turn them out onto a cooling rack and cool completely.
Wrap in plastic wrap and chill until ready to use.