Preheat the Oven:
Preheat your oven to 375°F (190°C).
Line baking sheets with parchment paper or silicone baking mats.
Mix the Dough:
In a large mixing bowl, cream together the softened butter and 1 1/2 cups of granulated sugar until light and fluffy.
Add the eggs one at a time, beating well after each addition.
Combine Dry Ingredients:
In a separate bowl, whisk together the flour, cream of tartar, baking soda, and salt.
Gradually add the dry ingredients to the butter mixture, mixing until just combined.
Prepare Cinnamon-Sugar Mixture:
In a small bowl, mix together the 1/4 cup of granulated sugar and 2 teaspoons of ground cinnamon.
Form the Cookies:
Using a cookie scoop or spoon, form the dough into 1 1/2-inch balls.
Roll each ball in the cinnamon-sugar mixture until well coated.
Bake the Cookies:
Place the coated dough balls on the prepared baking sheets, spacing them about 2 inches apart.
Bake for 8-10 minutes, or until the edges are set and the tops are slightly cracked. The centers will still look soft, but they will continue to set as they cool.
Cool the Cookies:
Allow the cookies to cool on the baking sheets for a few minutes before transferring them to a cooling rack to cool completely.