Pre-heat your oven to 350*F.
Add the almond flour, coconut flour, arrowroot starch, cinnamon, xanthan gum, baking soda, baking powder and salt to a bowl. Whisk to combine. Set aside.
In another larger bowl, add the softened butter and sweeteners. Use a hand mixer to beat them together until light and fluffy.
Add the eggs and vanilla extract and beat again until well-combined.
Add the dry ingredients to the wet ingredients and use a spoon or spatula to combine. Mix until you get a nice thick batter.
Grease an 8x8 inch pan with butter or oil, then spread the batter over the bottom and even out the top.
Sprinkle with a mixture of the sweetener and cinnamon mentioned above.
Bake the cookie bars for 18-20min or until a toothpick comes out clean and the edges are lightly browned around the outside. (These firm up much more after cooling, so take that into account when deciding how soft/under-baked you want the center of your bars to be).
Let the snickerdoodle bars cool almost completely before attempting to slice them. Slice into 16 squares, sprinkle with a touch more of the topping mixture (optional) and then serve! Enjoy your Keto Snickerdoodle Cookie Bars!