Pre-heat the oven to 350º F, and fill muffin tins with cupcake liners.
In a large mixing bowl, whisk together the flour, xanthan gum, baking powder, baking soda, and salt. Set aside.
In a separate large bowl, beat the eggs well; add the sugar, and continue beating for about 30 seconds.
Add the vanilla extract and oil to the eggs, beating until well combined.
Gradually add the dry ingredients, alternating with the buttermilk, beating until everything is thoroughly combined. The resulting batter will be thin.
Pour the batter into the cupcake liners, one by one, until each one is about 2/3 of the way full.
Bake at 350° F for about 12-14 minutes, or 'til a toothpick inserted into the center of a cupcake comes out clean.
Remove the cupcakes from the oven, and cool completely on a wire rack before frosting and/or decorating.