Preheat your oven to 375°F. Line rimmed baking sheets with parchment paper and set them aside.
In a large bowl, place the butter, 3/4 cup granulated sugar, egg, and vanilla. Beat with a handheld mixer until light and fluffy.
Add the flour, xanthan gum, salt, 3/4 teaspoon ground cinnamon, baking soda, and cream of tartar to the wet ingredients, mixing to combine after each addition.
Divide the dough into 18 pieces of roughly equal size. Roll each piece of dough between your palms until it forms a ball, and then press into a disk.
Combine the cinnamon and sugar for the rolling mixture in a small bowl. Toss each disk in the cinnamon-sugar mixture until it is well-coated. Allow the dough to sit for 5 minutes to absorb the coating.
Roll each ball of dough in the cinnamon-sugar mixture once more, and arrange them about 2 inches apart on the lined baking sheets.
Place the rimmed baking sheets in the center of the preheated oven and bake for 8 to 10 minutes, or they are either pale but flat (8 minutes), or a tiny bit crisp around the edges (10 minutes).
Cool on the baking sheets for about 10 minutes, then transfer to a wire rack to cool completely.
Video
Notes
Originally published in 2011 (!). In 2017, photos, video, text all new; recipe largely unchanged; in 2022, text resources and some more photos added.