Preheat oven to 350°F/175°C. Line and grease three eight-inch pans or four seven-inch pans. Set aside.
Combine the dry ingredients (gluten-free flour, granulated sugar, sifted cocoa powder, baking soda, baking powder, salt, and instant espresso) in a large bowl. Whisk together and set aside.
In a separate, medium-sized bowl, add the water, buttermilk, vinegar, oil, eggs, and vanilla extract. Whisk the ingredients together until combined.
Pour the wet ingredients into the dry ingredients. Whisk the batter for several minutes to give it some additional structure. Don't be afraid of over mixing, there's no gluten!
Cover the bowl with plastic wrap and let the batter sit for 30 minutes. This gives the gluten free flour time to absorb the liquids in the batter which can help prevent a gritty texture.
Divide the batter evenly between the prepared cake pans and bake for 25-27 minutes.
Remove from the oven and let the layers cool in the pans for about 10 minutes. Gently run an offset spatula around the rim of the cake pans to loosen them.
Place the cake pans in the freezer to speed up the cooling process and to trap in additional moisture.