Preparation

• In a medium bowl, toss together the flour, cream of tartar, cinnamon, baking soda, and salt. Set aside.
• In a large bowl with a handheld mixer or the bowl of a stand mixer fitted with the paddle attachment, 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. When all of the flour mixture has been added, 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. If chilling longer than 1 hour, allow to sit at room temperature for 10-15 minutes before moving on with the recipe.
• When you are ready to bake the cookies, preheat the oven to 350ºF (177ºC). Line a large baking sheet with parchment or a silicone baking mat and set aside.
• Toss together the granulated sugar and ground cinnamon for the cookie dough coating in a small bowl and set aside.
• 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.
• Cookies stay fresh stored in an airtight container at room temperature up to 7 days. Cookies freeze well, up to 2 months. Rolled cookie dough freezes well, up to 2 months. Thaw on baking sheet for 10 minutes, roll in cinnamon-sugar, and bake as directed.