Preheat your oven to 350°F (175°C) and line a baking sheet with baking paper.
In a medium mixing bowl, combine almond flour, coconut flour, sweetener, baking powder, cream of tartar, and salt. Stir until well mixed.
In a separate large bowl, beat the softened butter until creamy. Add the egg and vanilla extract and mix until smooth.
Gradually add the dry ingredients into the wet ingredients, mixing until a soft dough forms.
In a small bowl, mix the sweetener and cinnamon for the coating.
Scoop about a tablespoon of dough, roll it into a ball, and roll it in the cinnamon-sweetener mixture to coat.
Place the coated dough balls on the prepared baking sheet, spacing them about 2 inches apart. Gently flatten each ball slightly with your fingers or the bottom of a glass.
Bake for 12-15 minutes or until the edges are golden. The centers may appear soft but will firm up as they cool.
Allow the cookies to cool on the baking sheet for 10 minutes before transferring them to a wire rack to cool completely.