Spray a 9x13-inch oven safe baking dish with cooking spray. Whisk together gluten free all purpose baking flour and xanthan gum until well blended. Add rest of dry ingredients and mix well. Add beaten eggs, oil and vanilla to dry ingredients and mix well. Add nuts and raisins if desired.
Spread batter into prepared pan and bake for 20-25 minutes, or until lightly browned. Middle may appear soft but will become firmer while cooling. Let cool 20-30 min. before cutting into bars.
Wheat version: use 2 cups regular all purpose flour (or a blend of whole wheat and all purpose), no xanthan gum and increase salt to 1 tsp.