Blend the cottage cheese in a small blender or food processor until completely smooth.
In a large bowl, beat the butter and sweetener until creamy. Add the blended cottage cheese, egg yolk, and vanilla, and beat until smooth.
In a separate bowl, whisk together the almond flour, cream of tartar, baking soda, xanthan gum, and salt. Stir into the wet mixture until a soft dough forms, then chill for 30 minutes.
Preheat the oven to 350°F and line a baking sheet with parchment paper. In a small bowl, mix the sweetener and cinnamon for the coating.
Roll the dough into 1 1/2 tbsp balls, then roll each ball generously in the cinnamon coating. Place them 2 inches apart and press down to about 1/2 inch thick.
Bake for 12 to 14 minutes, until the edges are lightly golden and the tops are slightly crackled.
Cool on the baking sheet for 15 minutes before moving them to a wire rack.