Preheat your oven to 325 degrees F. Spray three 8-inch or four 6-inch pans with nonstick spray, line the bottom of the pans with parchment paper and spray again. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, sugar, cocoa powder, baking soda, baking powder and salt. Stir to combine.
In a separate bowl, combine the buttermilk, vegetable oil, eggs, water and vanilla. Stir until combined.
With the mixer on low speed, slowly add the wet ingredients to the dry ingredients. Mix for about 30 seconds and then scrape down the sides of the bowl Mix again for 10-20 seconds until the ingredient are combined.
Evenly distribute the batter among the pans. For three 8-inch pans, I usually get about 15-16 ounces in each pan. For the four 6-inch pans, about 12 ounces in each pan.
Bake for 20 to 25 minutes
Let cool in the pans for about 10 minutes before inverting onto cooling racks to cool completely.
Once cooled completely, the cakes can be individually wrapped in plastic wrap and stored in the freezer for a few days. If you want to store the cakes for longer, wrap each in foil as well. With the foil, the cake layers will be good for about a month.