Gluten Free Millet Rice Tapioca Cookies

113 g unsalted butter
100 g granulated sugar
1 extra large egg
1 tsp vanilla extract
100 g white rice flour
80 g millet flour
40 g tapioca flour
1 tsp baking powder
1/4 tsp salt

Cream the butter with the sugar.  Add in the egg and vanilla extract and mix well.  Blend the flours with the salt and baking powder.  Gradually add the dry mixture.  Drop by teaspoonfuls onto a cookie sheet.  Bake for 8-10 min at 350 degrees F, until lightly browned.  Cool.