Preheat the oven to 350°F. Line a large baking sheet with parchment paper. Set aside.
In a medium bowl, whisk together the flour, cream of tartar, baking soda, and kosher salt. Set aside.
2¾ cups all-purpose flour, 2 teaspoons cream of tartar, 1 teaspoon baking soda, ½ teaspoon kosher salt
In a large mixing bowl, use a hand mixer to cream the butter and 1½ cups granulated sugar for about 2 minutes.
1 cup unsalted butter, 1½ cups granulated sugar
Add the eggs and vanilla extract. Mix until smooth and completely combined.
2 large eggs, 1 teaspoon vanilla extract
Add the dry ingredients to the butter mixture. Mix until completely combined and a cookie dough forms.
Using a 1-Tablespoon cookie scoop, portion out the dough. Roll each portion between your hands to form a ball about 1 inch in diameter.
Combine ⅓ cup granulated sugar and the cinnamon in a small, shallow dish.
⅓ cup granulated sugar, 2 tablespoons ground cinnamon
Place each cookie dough ball into the cinnamon sugar mixture and use a spoon to coat it completely.
Arrange the dough balls on the prepared baking sheet, spacing them about 2 inches apart.
Bake for 9 to 12 minutes. My cookies were best around 10 to 11 minutes. The edges should look set, the tops should be slightly cracked, and the centers should still look puffed and soft.
Let the cookies cool on the baking sheet for about 5 minutes. They will flatten and continue to set as they cool.
Transfer the cookies to a wire rack and allow them to cool completely.