Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats to prevent sticking and allow for even baking.
In a large mixing bowl, beat the softened unsalted butter and 1 1/2 cups granulated sugar together using a hand or stand mixer on medium speed until light, fluffy, and pale in color, about 3-4 minutes.
Crack in the eggs one at a time, mixing well after each addition to add moisture and bind the dough.
In a separate bowl, whisk together the all-purpose flour, cream of tartar, baking soda, salt, and 1 tablespoon ground cinnamon to evenly distribute ingredients.
Gradually add the dry ingredients to the butter mixture, mixing on low speed until just combined. Avoid overmixing to keep cookies soft and tender.
In a small bowl, combine the remaining 1/4 cup granulated sugar and 1 tablespoon ground cinnamon for the cookie coating.
Use a cookie scoop or spoon to portion dough balls about 1.5 tablespoons each. Roll each ball in the cinnamon-sugar mixture until fully coated.
Place coated dough balls on the prepared baking sheets, spacing about 2 inches apart. Bake for 10-12 minutes until edges are lightly golden but centers remain soft and puffy.
Remove from oven and let cookies cool on the baking sheet for 5 minutes before transferring to a cooling rack to set.