Preheat oven to 350°F. Grease and line 2 (8-inch round) cake pans with parchment paper. Grease again. (I used non-stick cooking spray). Set aside.
Measure out dry ingredients (gluten free flour, cocoa, baking powder, xanthan gum and salt) into a bowl and whisk together until combined. Set aside. (Note: if you don't want it to be gluten free, substitute the same amount of all purpose flour and omit the xanthan gum.)
Combine cooled coffee and vanilla in a large measuring cup. Set aside.
In a large bowl, cream together the butter and sugar with an electric mixer on medium until light and fluffy. Turn mixer to low and add the eggs, one at a time. Turn mixer back up to medium and beat for 30 seconds.
Turn mixer down to low and alternate adding your dry ingredients and liquid ingredients. Once all of these ingredients are combined, turn mixer up to medium and beat for 2 minutes.
Pour into prepared pans and bake for 40-45 minutes or until a toothpick inserted into middle comes out clean. Let cool completely. Remove cakes from pans. If there is a dome top, cut the domed part off with a large, serrated bread knife (cutting horizontally). You just want your cakes to be flat on top. If the cake is gluten free, there won't be a domed top.