Gluten-Free Shortbread

white rice flour ( (5 1/3 ounces; 151 grams))

sweet rice flour ((2.5 ounces/ 70 grams) )

cornstarch ( cup cornstarch (2 ounces/ 56 grams))

salt

baking powder

xanthan gum (this prevents the cookies from spreading)

butter, softened ((7 ounces; 198 grams))

granulated sugar ((5 1/4 ounces; 148 grams))

vanilla extract