Whisk together white rice flour, cornstarch, sweet rice flour, baking powder, xanthan gum,and salt.
Cream together sugar, butter, and vanilla in a large mixing bowl until a thick paste forms, about 1 minute. Add eggs, one at a time, and mix until well combined. Reduce speed to low and add the dry ingredients. Mix for 45 seconds.
Remove cookies from the oven and allow to cool for 3 minutes on the baking sheet. After 3 minutes, transfer cookies to a wire rack to cool. Store cookies in an airtight container.