Preheat oven to 375°F (190°C). Line baking sheets with parchment paper.
In a medium bowl, whisk together flour, cream of tartar, baking soda, and salt.
2.75 cups all-purpose flour
In a large bowl, beat butter and 1.5 cups sugar until fluffy. Add eggs one at a time, then vanilla extract and mix well.
2.75 cups all-purpose flour
Gradually add dry ingredients to wet mixture, blending until combined.
In a small bowl, mix 0.33 cup sugar with cinnamon for coating.
2.75 cups all-purpose flour
Shape dough into 1.5 inch balls, then roll in cinnamon sugar mixture. Place on prepared baking sheets 2 inches apart.
Bake for 8-10 minutes or until edges are set but centers are soft. Allow cookies to cool on baking sheet for 5 minutes before transferring to wire rack.
Notes
Store cookies in an airtight container for up to one week. Perfect with a glass of milk or hot tea.