Preheat the oven to 350F and grease an 8x8 pan.
In a bowl whisk together sorghum flour, almond flour, corn starsh, tapioca starch, xanthan or guar gum, baking soda, baking powder, salt, cinnamon and nutmeg.
In bowl of mixer, whisk melted shortening with brown sugar and the egg until well creamed and fluffy.
Add gluten free flour mixture to sugar mixture. Stir until well combined. It will be thick.
Fold in apples and walnuts. Spread the batter into the prepared pan.
Bake for 35 (mine took 40) minutes or until a tester comes out clean. Let cool before cutting into 16 squares.