- 1 3⁄4 cups sugar
- 1 tablespoon ground cinnamon
- 2 1⁄2 cups all-purpose flour
- 2 teaspoons cream of tartar
- 1 teaspoon baking soda
- 1⁄2 teaspoon table salt
- 8 tablespoons unsalted butter, softened (1 stick)
- 1⁄2 cup vegetable shortening
- 2 large eggs
Adjust an oven rack to the middle position and heat the oven to 375 degrees. Combine 1/4 cup of the sugar and the cinnamon in a shallow dish for coating and set aside. Whisk the flour, cream of tartar, baking soda, and salt together in a large bowl and set aside.
Beat the butter, shortening, and remaining 1 1/2 cups sugar together in a large bowl using an electric mixer on medium speed until light and fluffy, 3 to 6 minutes. Beat in the eggs, one at a time, until incorporated, about 30 seconds, scraping down the bowl and beaters as needed.
Reduce the mixer speed to low and slowly mix in the flour mixture until combined, about 30 seconds. Give the dough a final stir with a rubber spatula to make sure it is combined.
Using wet hands, roll 2 tablespoons of dough at a time into balls, then roll in the cinnamon sugar to coat and lay on two parchment-lined baking sheets, spaced about 2 1/2 inches apart. Bake the cookies, one sheet at a time, until the edges are set and just beginning to brown but the centers are still soft and puffy, 10 to 12 minutes, rotating the baking sheet halfway through baking.
Let the cookies cool on the baking sheet for 10 minutes, then serve warm or transfer to a wire rack and let cool completely.
To Make Ahead: The dough can be made through step 3 and either covered tightly with plastic wrap and refrigerated for up to 3 days or frozen. To freeze the cookie dough, portion into individual balls, roll in the cinnamon and sugar, and freeze on a parchment- or wax-paper-lined plate (don’t let them touch or they will fuse together) until completely firm, 2 to 3 hours. When ready to bake, reduce the oven temperature to 300 degrees and increase the baking time to 17 to 22 minutes.