01 - Preheat oven to 350°F and line two baking sheets with parchment paper.
02 - In a medium bowl, whisk together gluten-free flour blend, baking soda, cream of tartar, and sea salt until evenly distributed.
03 - In a large bowl, beat softened butter and granulated sugar with an electric mixer until light and fluffy, approximately 2 minutes.
04 - Add the large egg and vanilla extract to the butter mixture, mixing until fully combined and smooth.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed just until a soft dough forms. Avoid overmixing.
06 - In a small bowl, combine the remaining 1/2 cup granulated sugar and ground cinnamon, stirring until thoroughly mixed.
07 - Scoop dough by tablespoonfuls and roll into balls. Roll each ball generously in the cinnamon-sugar mixture until completely coated.
08 - Place coated dough balls 2 inches apart on prepared baking sheets, allowing room for spreading.
09 - Gently press down on each dough ball with your palm or the bottom of a glass to flatten slightly.
10 - Bake for 9 to 11 minutes, or until edges are firm and tops appear slightly crackled. Centers should still be soft.
11 - Let cookies rest on baking sheets for 5 minutes, then transfer to a wire rack to cool completely before serving.