Preheat the oven to 375°F (190°C). Line two baking sheets with parchment paper.
In a medium bowl, whisk together flour, cream of tartar, baking soda, and salt. Set aside.
In a large bowl, cream the butter and sugar together until light and fluffy, about 2–3 minutes.
Add the eggs and vanilla extract, mixing until fully combined.
Gradually add the dry ingredients to the wet mixture and mix just until combined.
In a small bowl, combine cinnamon and sugar for the coating.
Roll tablespoon-sized portions of dough into balls and coat them generously in the cinnamon-sugar mixture.
Place the coated dough balls on prepared baking sheets, 2 inches apart.
Bake for 9–11 minutes, until the edges are set but the centers are still soft.
Allow cookies to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.