In a medium-sized bowl, whisk the GF flour, black cocoa, baking powder, baking soda, and salt together. In a large bowl using a hand/stand mixer, mix the sugar and oil together. Add the eggs and mix very well for 1-2 minutes, until it becomes more pale in color. Add half of the dry mixture and mix until combined. Add the vanilla and milk of choice and mix well. Add the rest of the dry mixture and mix until combined. Scrape the sides and bottom of the bowl with a spatula. While mixing on low, carefully pour in the boiling water and mix until very well combined.