Preheat oven to 350. Lightly grease 9" square pan, line with parchment paper.
Portion size3 servings
1. Prepare base: in food processor, pulse rice flour, cornstarch, tapioca starch, xanthan gum, sugar, salt and coconut. Add butter and pulse until mixture resembles small peas, about 5-10 seconds. With machine running, add egg through feed tube. Process until dough just forms a ball. Spread evenly in bottom of pan. Remoisten when dough begins to stick to spatula. 2. Bake in preheated oven for 12-15 minutes, or until set. Reduce oven temp to 325. 3. Meanwhile prepare the topping. In a bowl, using electric mixer, beat eggs, sugar coconut, lemon zest, juice, cornstarch and baking powder until blended. Pour over hot base. 4. Bake for 40-45 minutes or until lightly browned and firm to the touch. Let cool completely in pan on a rack. Cut into squares.