Preheat oven to 350 degrees and spray two 4-inch ramekins with non-stick spray.
In a medium bowl, whisk together the egg, pumpkin, sugar, oil, and vanilla.
Sift in the flour, xanthan gum, baking powder, baking soda, salt, cinnamon, and nutmeg. Stir to combine and make sure all the dry ingredients are mixed in.
Pour the batter evenly between the two ramekins and place the ramekins on a rimmed baking sheet (for easily getting them in and out of the oven). Bake at 350 degrees for 22-26 minutes or until a cake tester comes out clean.
Cool on a wire rack, remove cakes from ramekins after 10 minutes to cool completely before frosting or freezing.