Step 1

In a large mixing bowl, whisk together flour, baking powder, soda, cream of tartar and salt. Set aside.

Step 2

Place butter in a glass microwave-safe bowl. Microwave for 20 seconds, check and microwave for 10 more seconds if needed. See note for tips!

Step 3

Cool butter completely. Add both sugars and whisk for 20 to 30 seconds. Add egg and vanilla and whisk just until combined.

Step 4

Add dry ingredients to wet ingredients and stir with a wooden spoon until all ingredients are combined.

Step 5

Cover the bowl with dough and chill for at least 30 minutes.

Step 6

Line a baking sheet with parchment paper or silicone baking mat.

Step 7

Preheat oven to 350 degrees F.

Step 8

In a small mixing bowl or ramekin, combine granulated sugar and cinnamon. Scoop the cookie dough with a 1.5-tablespoon size cookie scoop, roll into a ball and roll in cinnamon sugar. Place on prepared baking sheet, spacing the dough balls at least 2 inches apart.

Step 9

Bake cookies for 9 to 11 minutes. For me the magic number was 10 minutes exactly. The cookies will look puffed up but will deflate while cooling and will have the classic snickerdoodle folds.