Blend the cottage cheese in a small blender or food processor until completely smooth.
Beat the butter and sweetener until creamy, then beat in the blended cottage cheese, egg yolk, and vanilla. Add the almond flour, coconut flour, baking powder, xanthan gum, and salt, and mix into a smooth dough. Chill for 20 minutes.
Place the dough between two sheets of parchment paper and roll it into a rectangle about 8 x 10 inches. Peel off the top sheet.
Brush the melted butter over the dough. Mix the brown sweetener and cinnamon, then sprinkle it evenly on top.
Using the bottom parchment to help lift, roll the dough up tightly from the long side into a log. Pinch together any cracks. Wrap the log in the parchment and freeze for 30 minutes, until firm enough to slice.
Preheat the oven to 350°F and line a baking sheet with parchment paper. Slice the log into 1/2 inch rounds and place them 1 1/2 inches apart.
Bake for 12 to 14 minutes, until golden at the edges. Cool on the baking sheet for 15 minutes.
Whisk the powdered sweetener, cream cheese, heavy cream, and vanilla until smooth. Drizzle over the warm cookies and let set for 10 minutes.