Preheat oven to 350 degrees F.
Line a muffin cup tin with cupcake liners.
In a large bowl, stir together cocoa powder, cornstarch, sorghum flour, tapioca flour, xanthan gum, baking powder, baking soda and salt; set aside.
In a medium bowl, combine granulated sugar and oil; blend on medium.
Pour in the melted chocolate and stir.
Beat in the eggs one at a time.
In a third bowl, mix the food coloring and vanilla into the buttermilk and stir well.
Add all ingredients now to the flour mixture and blend on low (do not overbeat).
Fill each cupcake liner about 3/4 up.
Bake for 20-25 minutes.
Let cool completely.