Preheat oven to 350 degrees. On high speed beat the butter and sugar for 15 minutes, scraping down the sides of the bowl to ensure even mixing. Place the cupcake liners into the muffin pans. In a separate bowl, sift the flour, cocoa, baking powder, xanthan gum and sea salt. Add the eggs one at a time to the butter mixture, followed by the vanilla extract. Turn the mixing machine to low and gradually add the flour mixture, alternating with the sour cream and ending with flour. Fill the cupcake liners 1/2 way. Bake for 10 minutes and then rotate pans and bake for an additional 10 mins. Allow to cool in the pan for 5 minutes before transferring to a wire rack.
Makes 24 cupcakes