Preheat your oven to 375°F (190°C). Line baking sheets with parchment paper.
In a medium bowl, whisk together the flour, cream of tartar, baking soda, and salt. Set aside.
In a large mixing bowl, cream the softened butter and granulated sugar together until light and fluffy, about 3-4 minutes.
Beat in the eggs one at a time, mixing well after each addition. Add in the vanilla extract and mix until combined.
Gradually add the dry ingredients into the wet mixture. Stir until just combined, being careful not to overmix.
In a small bowl, mix 1/4 cup granulated sugar with the ground cinnamon.
Scoop tablespoons of dough and roll them into balls. Roll each ball in the cinnamon sugar mixture to coat completely.
Place the coated dough balls onto the prepared baking sheets, spacing them about 2 inches apart. Bake for 8-10 minutes, or until the edges are lightly golden and the centers are set but still soft.
Allow cookies to cool on the baking sheets for about 5 minutes before transferring them to a wire rack to cool completely.
Notes
Stack the cookies on a decorative plate, and sprinkle a little extra cinnamon sugar on top for a festive touch. Serve with a glass of cold milk!