Preheat oven to 400°F (205°C). Line a cookie sheet with parchment paper or a silicone baking mat.
In a medium bowl, whisk together flour, cream of tartar, baking soda, and salt. Set aside.
Beat butter and 1 1/2 cups sugar until light and fluffy, about 2–3 minutes.
Add eggs one at a time, mixing after each addition. Scrape bowl as needed. Mix in vanilla extract.
Add dry ingredients to wet ingredients and mix until just combined.
In a small bowl, mix remaining 3 tablespoons sugar with cinnamon.
Scoop 1 tablespoon dough portions, roll into balls, then coat in cinnamon sugar. Place 2 inches apart on baking sheet.
Bake for 6–8 minutes until edges are set but centers are soft.
Let cookies rest 2–3 minutes, then transfer to a cooling rack. Store in an airtight container.
