In a small bowl, whisk together the flour, xanthan gum, salt, 3/4 teaspoon ground cinnamon, baking soda, and cream of tartar.
In a separate large mixing bowl with a handheld mixer or the bowl of a stand mixer fitted with the paddle attachment, place the butter, and 3/4 cup granulated sugar. Beat at medium-high speed until light and fluffy (about 4 minutes), scraping down the mixer at least once.
Add the egg and vanilla and beat at medium speed just until fully combined (1 minute or less).
Add the whisked dry ingredients to the wet ingredients in the mixing bowl, and mix on medium-low speed until just combined (about 1 minute).
The cookie dough will be soft and fluffy, but sticky. Transfer it with a spatula to a large sheet of plastic wrap and close the plastic tightly.
Chill the cookie dough for at least 1 hour and up to 2 days, until mostly firm.
Shape and coat the dough
Line rimmed baking sheets with parchment paper and set them aside.
Unwrap the chilled cookie dough and divide the chilled dough into 12 pieces of roughly equal size.
Roll each piece of dough lightly between clean palms until it forms a ball, then place on a prepared baking sheet, about 2 inches apart from one another.
Combine the cinnamon and sugar for the rolling mixture in a small bowl. Toss each ball of dough in the cinnamon-sugar mixture until it is well-coated, then replace it on the baking sheet.
Preheat your oven to 375°F.
Allow the dough to sit for 5 minutes to absorb the coating, then repeat the process, tossing each piece of dough in the rolling cinnamon-sugar again and replacing on the baking sheet.
Bake
Bake in the center of the preheated oven for about 10 minutes, or until the cookie dough has spread into a round and is no longer glistening in the center.
Cool on the baking sheets for about 10 minutes, then transfer to a wire rack to cool completely.
Video
Notes
Flour blend notes – I recommend Better Batter's classic blend without adding xanthan gum, Nicole's Best multipurpose plus xanthan gum, Bob's Red Mill 1-to-1 gluten free (in the blue bag) with an added 1/8 teaspoon xanthan gum. Vitacost Multi-Blend gluten free flour plus xanthan gum also works very well. For a DIY version of Better Batter or the original Cup4Cup blend, which would work well here, too, see our all purpose gluten free flour blends page.