Preheat oven to 375°F (190°C) and line baking sheets with parchment paper.
Whisk together flour, cream of tartar, baking soda, and salt in a bowl.
In another bowl, beat butter and sugar until light and fluffy.
Add eggs and vanilla extract and mix until fully combined.
Gradually mix dry ingredients into wet ingredients until a soft dough forms.
In a small bowl, combine sugar and cinnamon for coating.
Scoop large dough balls and roll each in cinnamon sugar mixture.
Place on baking sheet leaving space between each cookie.
Bake for 10–12 minutes until edges are set but centers remain soft.
Cool on baking sheet for 5 minutes before transferring to a wire rack.
