1. In a large mixing bowl, whisk together the flour, baking soda, cream of tartar, cinnamon and salt. In the bowl of a stand mixer fitted with the paddle attachment, beat together the butter and both sugars on medium-high for 2 minutes, or until soft and fluffy. Add the egg and egg yolk and beat to combine, using a spatula to scrape down the sides as needed. Add the vanilla extract and combine.
2. With the mixer running on low, slowly add the dry ingredients until a soft cookie dough forms. Cover and refrigerate the dough for at least 1 hour**. Remove the dough from the fridge, and using a medium cookie scoop (about 1 tablespoon), scoop the dough out and using your finger, create an indent. Place one caramel half in the middle, then push the dough up and over the caramel to cover it. Roll the dough in your hands to form a ball, then roll the ball in the cinnamon sugar mixture, rolling twice to ensure the dough is completely covered. Place the balls of dough on a baking sheet prepared with parchment paper, about 2 inches apart. Place the entire tray in the fridge for 30 minutes to chill.
3. Preheat the oven to 350 F. After chilling for 30 minutes, remove the dough from the fridge and place it directly into the oven to bake for 10-11 minutes. Cookies are done when the outsides are firm but the middle looks slightly under-baked. Remove the cookies and let them cool for 5 minutes on the tray. Sprinkle extra cinnamon sugar on top. Use a spatula to remove the cookies to a wire rack to cool completely.

Cookies can be stored at room temperature in an airtight container for up to 1 week, or in the freezer for up to 2 months.