Snickerdoodles

Ingredients (Cookies)

1 cup (2 sticks or 230g) unsalted butter, softened to room temperature
1 and 1/3 cup (267g) granulated sugar
1 large egg
2 teaspoons vanilla extract
3 cups (375g) all-purpose flour (measured correctly)
2 teaspoons cream of tartar*
1 teaspoon baking soda
2 and 1/2 teaspoons ground cinnamon
1/2 teaspoon salt

Ingredients (Toppings)

1/4 cup (50g) granulated sugar
1 teaspoon cinnamon

Recipe (Topping)
1. Toss 1/4 cup granulated sugar with 1 teaspoon cinnamon in a small bowl. Set aside.

Recipe (Cookies)
1.Preheat oven to 375F degrees.
2. Line two large cookie sheets with parchment paper or silicone baking mats. Set aside.
3. In a large bowl using a hand-held mixer or stand mixer with paddle attachment, cream the softened butter for about 1 minute on medium speed.
4. Get it nice and smooth, then add the sugar on medium speed until fluffy and light in color.
5. Mix in egg and vanilla. Scrape down the sides as needed. Set aside.
6. In a medium size bowl, whisk together the flour, cream of tartar, baking soda, cinnamon, and salt.
7. With the mixer running on low speed, slowly add the dry ingredients to the wet ingredients in 3 different parts. The dough is quite thick and you may have to stir the rest by hand.
8.  Take 1.5 - 2 Tablespoons of dough and roll into a ball. Roll the dough balls into the reserved cinnamon-sugar topping. Sprinkle extra cinnamon-sugar on top if desired.
9. Bake cookies for 11-12 minutes. The cookies will be very puffy and soft.
10. When they are still very warm, lightly press down on them with the back of a spoon or fork to help flatten them out. Allow cookies to cool on the baking sheet for 10 minutes and transfer to a wire rack to cool completely.

Notes:
This recipe is from here. 
Cookies remain soft & fresh for 7 days in an airtight container at room temperature.
Make ahead tip: There are a few options here! First, you can prepare the cookie dough and chill it in the refrigerator for up to 3 days. Make sure that you let it come to room temperature before rolling and baking the cookies. You can also freeze the cookie dough balls. Roll the dough into balls then freeze the balls for up to 2-3 months. You can freeze the cookie dough balls with the cinnamon sugar coating or without, your call. When ready to make, bake the frozen cookie dough balls 1-2 minutes longer than what the recipe states. You can also freeze the baked cookies for up to 3 months. Thaw overnight in the refrigerator before serving.