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