Oooh, I've also seen something similar done w/ brownies!

What is the correct way to prepare this recipe with all-purpose flour?

To convert "back" to wheat-flour, eliminate the xanthan gum and decrease the total flour to swap for the gluten-free flours. In this recipe, that means using about 2 cups.

UPDATE: The above conversion works for most gluten-free -changing back to wheat, especially cakes. But this recipe's original started out using 2 1/4 cups (wheat) bread flour (which has more gluten content than All Purpose flour).