Start by mixing all the sugar and spice coating ingredients in a small bowl. Set it aside, you’ll need it soon!
In a medium bowl, whisk together the flour, baking soda, cream of tartar, and salt.
In a large bowl, beat the butter and sugar on medium-high for about 2 minutes, until it’s light, fluffy, and smells amazing.
Add the egg and vanilla, then beat on low for about 30 seconds until everything is nicely combined.
Gently fold in the dry ingredients with a spatula until you get a soft, dreamy cookie dough.
Scoop out 2-tablespoon balls of dough, roll them in your sugar-spice mixture, and pop them in the fridge for 15–20 minutes, lightly covered with plastic wrap.
Preheat your oven to 350°F and line two baking sheets with parchment paper.
Place the chilled dough balls on the sheets, leaving about 2 inches between each cookie, they’ll need their space!
Bake for 8 minutes, until the edges are golden but the tops are still soft. Let them cool on the baking sheet for 5 minutes, then gently press a small indentation into each cookie with a spoon or your thumb.
Transfer to a wire rack and let them cool completely, about 1 hour—before enjoying your perfectly chewy snickerdoodles.