Preheat oven to 350°F and line a standard muffin pan with 12 paper liners or spray with non-stick spray.
In a medium bowl, whisk together the gluten free flour, xanthan gum, granulated sugar, baking powder, and salt. Set aside
In a large bowl, whisk together the egg, sour cream, milk, oil, vanilla extract, and butter extract. Add the dry ingredients and stir to combine.
Divide the batter evenly between the 12 muffin cups and bake for 18-22 minutes or until done.
Remove from the baking pan and cool completely on a wire rack.
When cool, frost with frosting of choice.
Notes
For dairy free, use plain dairy free yogurt in place of the sour cream, use unsweetened coconut milk in place of the regular milk, and reduce the xanthan gum to 1/4 teaspoon.
Canola or vegetable oil can be used in place of avocado oil.