Preheat Oven: Preheat oven to 375°F (190°C). Line baking sheets with parchment paper.

Mix Dry Ingredients: In a medium bowl, whisk together flour, cream of tartar, baking soda, and salt. Set aside.

Cream Butter and Sugar: In a large bowl, beat butter and 1 ½ cups sugar with an electric mixer until light and fluffy. Add eggs one at a time, beating well after each addition. Mix in vanilla extract.

Combine Dry and Wet Ingredients: Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Prepare Cinnamon-Sugar Coating: In a small bowl, mix ¼ cup sugar with 2 tsp cinnamon.

Shape the Cookies: Scoop 1–2 tbsp of dough and roll into balls. Roll each ball in the cinnamon-sugar mixture until fully coated.

Bake the Cookies: Place coated dough balls on prepared baking sheets about 2 inches apart. Bake 10–12 minutes, or until edges are lightly golden and tops are cracked.

Cool: Let cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.