-
Preheat oven to 350°F. Spray 9-inch baking pan with gluten-free cooking spray.
-
In small mixing bowl, whisk together white rice flour, cornstarch, sweet rice flour, salt, baking powder, and xanthan gum. Set aside.
-
In medium mixing bowl, cream together butter, and dark brown sugar until thick paste forms, about 30 seconds. (Use high speed on handheld mixer or medium-high speed on stand mixer.) Add egg and mix until thoroughly combined.
-
Add whisked dry ingredients. Blend until smooth, about 30 seconds. (Use medium-high speed with a handheld mixer or medium speed with a stand mixer.) Batter will be dry. Add maple syrup and vanilla. Mix until batter is light and fluffy.
-
Spread batter evenly into prepared pan. Bake until golden brown, about 25-30 minutes. Remove pan from oven and place on wire rack to cool completely. When cool, Cut into nine or 12 pieces.