Butter a 9x13-inch baking dish.
In a small bowl, whisk together sugar and cornstarch, set aside. In a large covered saucepan, heat cherries over medium heat with the lid on for 10 to 15 minutes, stirring often. Once fruit has released it juice, pour sugar mixture over the fruit and stir thoroughly to combine. Reduce heat to low. Bring to a simmer, and cook until thickened stirring continuously, about 2 minutes. Remove from heat and let stand 15 minutes.
Preheat oven to 350 F.
In a large mixing bowl sift together rice flour, tapioca flour, salt, baking soda, baking powder, xanthan gum, and cinnamon. Using a fork or pastry blender, cut butter into flour mixture until it resembles coarse crumbs.
Pour fruit mixture into prepared baking dish. Spread the rice mixture evenly over the top of the fruit. Place in pre-heated oven and cook 45 to 50 minutes until top is golden brown and filling is bubbling around the edges.
Serves 10 to 12