Preheat oven to 350°F and line a muffin tin with 4 paper liners or spray with non-stick spray.
In a medium sized bowl, whisk together flour, xanthan gum, cocoa powder, sugar, baking powder and baking soda. Form a well in the middle of the dry ingredients by pushing the mixture to the sides of the bowl.
In the middle of the well, whisk together the canola oil, vanilla extract, and buttermilk. Slowly stir in the dry ingredients until completely incorporated. Stir in coffee.
Divide the batter equally between the 4 cups and bake 15-17 minutes or until a cake tester comes out clean. Mine took 17 minutes. Cool cupcakes completely before frosting.
For the Frosting:
Beat together the butter, Nutella and powdered sugar in the bowl of a stand mixer fitted with the paddle attachment (or with a handheld mixer). Beat at medium speed for two minutes.
Scrape down the bowl and add the vanilla extract and heavy cream. Beat on medium speed for an additional minute. Spread or pipe frosting onto the cooled cupcakes and garnish with sprinkles or decorating sugar if desired. Enjoy!