Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking pan.
Stir rice flour, tapioca flour, cocoa powder, potato flour, xanthan gum, and salt together in a bowl.
Mix sucanat and butter together in a large bowl with an electric mixer on medium speed until creamy. Stir in applesauce. Add eggs and mix until fluffy. Mix in vanilla extract, baking soda, baking powder, and salt. Add flour mixture and stir until combined. Stir in chocolate chips. Press dough into the greased baking pan using a butter wrapper.
Bake in the preheated oven until top is lightly browned, about 25 minutes.