Preheat the oven to 400°F. Line a 9”x9” metal baking pan with parchment paper, and spritz with nonstick baking spray. Set aside.
In a small bowl stir the 1½ tablespoons of sugar with the cinnamon and set aside.
1 ½ tablespoons granulated sugar, 1 teaspoon ground cinnamon
In a medium bowl, whisk together the flour, cream of tartar, baking soda, and salt. Set aside.
1 ⅓ cups flour, 1 teaspoon cream of tartar, ½ teaspoon baking soda, ¼ teaspoon salt
In a separate bowl, cream together the softened butter, ¾ cup of sugar, and the egg with a mixer until light and fluffy.
½ cup unsalted butter softened, ¾ cup granulated sugar, 1 egg
Add the flour mixture to the butter mixture, mixing until just combined. Do not overmix.
Using your clean hands, press the cookie batter into the prepared baking pan.
Once the batter is evenly spread throughout the pan, sprinkle the mixture of cinnamon and the remaining 1 ½ tablespoons of sugar on top.
Bake in the preheated oven for 18-20 minutes, or until an inserted toothpick comes out clean. Don't overbake. They will be dry.
Let cool slightly before slicing and enjoying.