In a large mixing bowl, cream together the softened butter, coconut sugar, and zero calorie sugar until smooth and creamy (1-2 minutes).
To the large mixing bowl, add the room temperature egg and vanilla extract, mixing until well combined. Do not over beat.
In a separate bowl, mix together almond flour, oat flour, cinnamon, cream of tartar, baking soda, and salt.
Add the dry ingredients to the wet ingredients then fold them together until a thick and sticky cookie dough forms.
Cover with plastic wrap and chill for 45 minutes to 1 hour in your refrigerator. You can chill up to 24 hours as long as it's wrapped in plastic wrap so that the dough does not dry out.
When ready to cook, preheat the oven to 350 F and line two baking sheets with parchment paper.
In a small bowl, mix together the ingredients for the sugar coating.
Use a spoon to scoop out 2 tablespoons of the dough (about 2 tablespoons) and roll into balls. Roll each ball in the sugar coating until evenly coated and place on a baking sheet.
Bake at 350 F for 12 - 14 minutes, until the edges are golden brown and the center is slightly under baked.
Remove from the oven and let the cookies cool on the baking sheet for 5 minutes before transferring to a wire baking rack to finish cooling.
Notes
Use the spoon and level method, where you slowly fill your measuring cup with spoonfuls of flour and level it off, versus scooping and packing the flour in.
Use a 1 ½” cookie scoop to make perfectly sized dough balls.
Gently tap the baking pan on the counter after you remove it from the oven to deflate the cookies and give them that signature crinkly appearance.