Preparation

• In a medium bowl, toss together the flour, cream of tartar, cinnamon, baking soda, and salt. Set aside.
• In a large bowl, cream the butter and sugar together on medium speed until light and fluffy (approximately 2-3 minutes).
• Add the egg and vanilla extract and beat again until completely incorporated.
• Reduce mixer speed to low and add the flour mixture in two parts. Beat on medium-high speed until dough is completely combined. Cover tightly and chill in the refrigerator at least 1 hour or up to 3 days.
• Preheat the oven to 350ºF (177ºC). Line a large baking sheet with parchment or a silicone baking mat.
• Toss together the granulated sugar and ground cinnamon for the cookie dough coating in a small bowl.
• Using a cookie scoop, roll dough into balls. Drop each ball into the cinnamon-sugar coating and roll around to coat completely. Place on baking sheet, no more than 8 per sheet.
• Bake cookies for 10-12 minutes, or until edges just start to set. Remove from oven and allow to rest on baking sheet for 2 minutes. Transfer to a wire rack to cool completely.