Snickerdoodles, buttery cookies rolled in cinnamon-sugar, are a staple at bake sales and holiday gatherings. Their characteristic sour note comes from cream of tartar, which before the advent of baking powder was used in conjunction with baking soda as a leavening agent.
12 tablespoons unsalted butter (1 1/2 sticks), at room temperature
2 large eggs, at room temperature
1 teaspoon vanilla extract
Heat the oven to 350°F and arrange a rack in the middle. Place 1/4 cup of the sugar and the cinnamon in a small bowl and mix until evenly combined; set aside.
Combine flour, cream of tartar, baking soda, and salt in a large bowl and whisk to aerate and break up any lumps; set aside.
Combine butter and remaining 1 1/4 cups sugar in the bowl of a stand mixer fitted with the paddle attachment and beat on medium speed until light and fluffy, about 2 minutes. Add eggs and vanilla and continue beating until eggs are fully incorporated. Scrape down the sides of the bowl and add flour mixture. Mix on low speed until fully incorporated, about 20 seconds.
Form tablespoon-size balls of dough with your hands and roll them in the cinnamon-sugar mixture. Place on a baking sheet about 1 inch apart.
Bake cookies until golden brown and crackly on top but still soft in the middle, about 11 minutes. Immediately remove from the baking sheet and cool on a rack. Repeat with remaining dough.