Peel, cube and boil the sweet potatoes for 15-20 minutes (or until fork tender).
In a small bowl combine the cocoa, gluten free flour, baking powder, salt and cinnamon.
In a large bowl cream together the butter and sugar. Add the vanilla and egg.
Once the sweet potato is boiled, drain the water then use an electric hand mixer to puree the sweet potato. Add the sweet potato to the butter and sugar, mix well.
Add the dry ingredients and stir to combine.
Pour the brownie batter into a greased 8 inch x 8 inch baking dish.
Bake for 35-45 minutes (or until a toothpick inserted in the middle comes out clean).