Preheat oven to 325°F and prepare the lowest rack of your oven. Prepare 3 8-inch cake pans with parchment paper on the bottom of the pan. DO NOT grease the pans.
In the bowl of a stand mixer, whip the egg whites with the cream of tartar and 1/2 cup of granulated sugar on medium to high speed until stiff peaks are formed. Set aside.
In a large bowl, combine your egg yolks, water, oil, and vanilla extract. Whisk until frothy.
Sift your dry ingredients (gluten free flour, cocoa powder, baking powder, baking soda, salt) into the wet ingredients. Whisk until well combined.
Add the whipped egg whites in 3-4 batches to the rest of the ingredients and fold gently with a spatula or wire whisk until fully combined.
Pour the batter equally between the 3 8-inch pans. Remember, do not grease the pans!
Bake for about 35 minutes or until cake springs back when lightly pressed. Set aside to cool completely.
When cooled, gently run a knife around the edges of the pan to release the cake.