Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, baking soda, cream of tartar, and salt. Set aside.
In a large bowl, cream the softened butter and sugar together until light and fluffy (about 2–3 minutes).
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Gradually add the dry ingredients to the wet mixture, mixing just until combined. Do not overmix.
In a small bowl, combine the cinnamon and sugar for the coating.
Scoop dough into 1.5-inch balls and roll each one in the cinnamon sugar mixture
Place cookies on the baking sheet about 2 inches apart.
Bake for 10–12 minutes, until edges are set but centers remain soft.
Let cookies cool on the baking sheet for 5 minutes before transferring to a wire rack.