Preheat Oven & Prep Pans:
Preheat your oven to 375°F (190°C). Line two baking sheets with parchment paper or silicone baking mats.
Mix Wet Ingredients:
In a large bowl, cream together the softened butter and sugar until light and fluffy (about 2-3 minutes). Add eggs one at a time, beating well after each addition.
Combine Dry Ingredients:
In a separate bowl, whisk together flour, cream of tartar, baking soda, and salt.
Form Dough:
Gradually add the dry ingredients to the wet mixture and mix until fully combined and a soft dough forms.
Make Cinnamon-Sugar Coating:
In a small bowl, mix together the ¼ cup sugar and 1 ½ tablespoons cinnamon.
Shape Cookies:
Roll dough into 1 to 1.5-inch balls, then roll each ball in the cinnamon-sugar mixture to coat evenly.
Bake:
Place dough balls about 2 inches apart on prepared baking sheets. Bake for 8–10 minutes, or until edges are just set and the centers look slightly underbaked.
Cool:
Let cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.