• Preheat oven to 350ºF.

Make the Dough

• In a large bowl cream together room temperature butter, sugar, and light brown sugar using a mixing stand or hand-held mixer.
• Add in egg and vanilla extract. Mix until well combined. Set aside.
• In a medium sized bowl, whisk together cream of tartar, baking soda, salt, cinnamon, and flour.
• Add flour mixture to dough in 3 additions, mixing in-between until well incorporated.

Form the Cookies

• Use a cookie scoop or about 2 tbsp of dough to form balls and place on a plate. Freeze for 15 minutes.
• Whisk together cinnamon and sugar for the coating.
• Line a baking tray with parchment paper.
• Remove cookie dough balls from freezer, roll in cinnamon sugar coating, and place on baking sheet at least 2 inches apart.

Bake the Cookies

• Bake at 350ºF for 9 minutes. Open the oven and bang the baking sheet down on the oven rack a few times.
• Bake for 3 more minutes, open the oven and bang the sheet again. Place back into oven for another 3 minutes.
• Cookies should be golden brown on the edges with a soft center. Remove baking sheet from oven and let cool for 3-5 minutes, then transfer to a wired cooling rack.