Whisk together the almond flour, cream of tartar, baking powder and salt.
Add in the sugar and whisk again, then add in the melted butter and oat milk and stir until a dough forms. Put this in the fridge to chill.
Preheat the oven to 350F.
In a small dish, mix together the sugar and cinnamon for coating.
Portion the dough into either 4 large cookies or 8 small cookies, roll them into balls and coat generously with the cinnamon sugar.
Bake the cookies on a parchment lined baking sheet at 350F for 15-16 minutes, or until they are spread and cracked.
*Optional, use a cookie cutter to swirl around the outside of the cookies after the are done baking, this will help form them into perfect circles.
Let cool fully before eating!