Preheat the oven to 350°F/175°C. Line and grease three 8-inch cake pans with parchment paper and nonstick spray. Set aside.
Combine 2 cups all-purpose flour, 2 cups sugar, 3/4 cup cocoa powder, 2 tsp baking powder, 1 1/2 tsp baking soda, and 1 tsp of salt in a large bowl. Whisk together until combined.
Add 1 cup of buttermilk, 1 cup of water, 1/2 cup oil, 2 eggs, and 2 tsp vanilla extract in the dry ingriedents. Mix by hand until fully incorporated. The batter will be on the thin side, but that’s the consistency you're after!
Divide the batter evenly between the cake pans and bake for about 23-25 minutes. I like to use a kitchen scale to weigh the pans. It makes sure each pan has the same amount of batter and helps the cake layers bake up to be the same height.
Remove the cake layers from the oven and let them cool in the pans for about 10 minutes. Gently run an offset spatula around the rim of the cake pans to loosen them, then flip them onto wire racks to finish cooling.
These cake layers bake up pretty flat, so leveling them is optional. If you want to level them with a serrated knife, make sure to wait until the cake layers have fully cooled to room temperature. If you make these in advance, wrap and freeze them at this point.