01 - Preheat the oven to 375°F. Line two baking sheets with parchment paper.
02 - In a medium bowl, whisk together flour, cream of tartar, baking soda, and salt. Set aside.
03 - In a large bowl, beat the unsalted butter and granulated sugar using an electric mixer until light and fluffy.
04 - Add eggs one at a time, beating well after each addition. Mix in the vanilla extract.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing until fully incorporated.
06 - In a small bowl, combine granulated sugar and ground cinnamon for the coating.
07 - Shape dough into 1 1/2-inch balls. Roll each ball in the cinnamon-sugar mixture to coat evenly.
08 - Place coated dough balls on prepared baking sheets, spacing them 2 inches apart. Bake for 10 minutes or until edges are set but centers remain soft.
09 - Allow cookies to cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.