In a medium bowl, whisk together gluten-free flour, cream of tartar, baking soda, cinnamon, and salt.
In a large bowl, beat the softened butter and sugar until light and fluffy.
Beat in the egg until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until a dough forms.
Preheat oven to 350°F. Mix coating ingredients in a small bowl. Scoop dough by 1 1/2 tablespoons, roll into balls, then roll in the cinnamon-sugar mixture.
Place on a parchment-lined baking sheet, spacing 2 inches apart. Flatten slightly.
Bake for 10-12 minutes or until edges are set but centers are soft. Cool on the baking sheet for a few minutes before transferring to a wire rack.