Whisk the almond flour, cream of tartar, baking soda, and salt in a large bowl.

Beat the butter and ½ cup sweetener until fluffy, then add the egg and vanilla and beat until pale.

Stir the dry mix into the wet until a dough forms. Scoop 1‑inch balls and roll each in a mixture of the remaining sweetener and cinnamon.

Place on a parchment‑lined sheet, press to ½ inch thick, and bake at 350°F for 9 to 11 minutes. Cool on the sheet 5 minutes, then transfer to a rack.