Preheat oven to 375 degrees. Prepare a baking sheet with parchment paper or use a baking stone.
Whisk together almond flour, coconut flour, xanthan gum, baking soda, cream of tartar, and salt until well combined.
In an electric mixer, beat the butter for 1 to 2 minutes.
Then add monk fruit to the butter and continue to mix for 7 to 8 minutes until fluffy, scraping down the sides periodically. Mixing for this amount of time is essential as the texture of the butter will change.
Add the vanilla and egg to the butter and then mix until blended slightly. The mixture will not be even.
Slowly add dry ingredients, mixing until just incorporated.
In a small bowl, whisk together cinnamon and xylitol until blended.
Using a cookie scoop (about 2 tablespoons), divide the dough into equal portions. Then roll dough in the cinnamon mixture until coated evenly.
Place cookie on a baking sheet and press down to about ½ inch thickness. NOTE: these cookies will not spread.
Bake for 8 to 10 minutes until the cookies are set. Remove from oven but rest on cookie sheet for 5 to 7 minutes. Transfer cookies to cooling rack and then cool completely before storing in an airtight container.