In a saucepan, add custard ingredients and cook over low heat. Allow to bubble gently, then remove from the heat.
In a large bowl, add all cake dry ingredients. Sift together.
Add wet ingredients to custard and whisk to blend.
Pour wet ingredients into dry ingredients and mix.
Pour the batter into the cake pan and bake 30-45 minutes until done. *see notes
Baking time really will vary by pan size, if you are making sheet cake, thinner layer cakes, or cupcakes with this batter.
I have tested this recipe with King Arthur Measure for Measure GF, Bob's Red Mill 1 to 1 GF blend, and Authentic Foods Multi Blend. That doesn't mean others will not work, I just have not tested other flours.
If your gluten free flour blend doesn’t contain Xanthan Gum or Guar Gum, please add 1 teaspoon.
To make this recipe dairy-free, substitute the butter for vegan butter.
There are several great gluten free cocoa powder brands I like to use. Ghirardelli, Rhodelle, Anthony's, and Hershey.
This cake will keep up to 4 days in an air-tight container, or up to 4 months in the freezer.