Combine the rice flour, cornstarch, confectioners' sugar, baking powder, baking soda, cream of tartar, salt, and butter in the bowl of a food processor. Pulse until pea-sozed crumbles form. Add the egg, and pulse until the dough comes together. Form the dough into a ball and transfer to a pie plate. With your fingertips, press the dough evenly into the pie plate. Crimp the edges with your fingertips or a fork. Place in the refrigerator and chill for 30 minutes.