Preheat the oven to 350°F. Line a baking sheet with a silpat liner or parchment paper. Set aside.
In a large bowl, mix together the butter and sugar until smooth with a wooden spoon or spatula.
1 cup (2 sticks) salted butter, room temperature, 1 ½ cups white sugar
Stir in the eggs and vanilla extract until combined.
2 eggs, room temperature, 1 teaspoon vanilla
Add the flour, cornstarch, cream of tartar, baking soda and cinnamon. Gently mix until all the flour is incorporated. Don't over-mix the cookie batter.
In a shallow bowl, mix together the topping ingredients until combined.
⅓ cup sugar, 1 Tablespoon cinnamon
Using a small cookie dough scoop, drop 1 ½ inch balls of dough into the cinnamon sugar mixture (see notes). Gently roll around until all the sides are coated and you have a ball shape. It’s okay if the dough balls are not perfectly round, the baking process should fix this! Place each coated dough ball on the prepared baking sheet 2 inches apart. If desired, sprinkle additional cinnamon sugar on top of each dough ball.
Bake for 9-10 minutes, or until the cookies are very puffed and cracked on top. The middle will be very soft and that’s okay. The cookies will continue to bake on the baking sheet outside of the oven. Don’t over bake or you won’t have a soft chewy cookie!
Allow the cookies to cool for 10 minutes (or until set) on the baking sheet then move the cookies to wire cooling racks.
Store at room temperature in an airtight container for up to 1 week or the freezer for up to 3 months.
Notes
Ingredient Tips - Add ¼ teaspoon salt to the batter (with the dry ingredients) if using unsalted butter.Prep Tips - The cookie dough should be soft, but not sticking to your hands. If the cookie dough is too sticky, place the cookie dough in the fridge for 30 minutes then try scooping and rolling in the cinnamon sugar mixture again.Baking Tips - If using a bigger cookie dough scoop (2 ½ Tablespoons), bake for 11-12 minutes, or until they are very puffed and cracked on top. Don’t over bake! Using this size scoop will make 18-20 cookies. Cinnamon Sugar Tips - If you have extra cinnamon sugar, sprinkle it on sourdough bread toast or use it in our cinnamon swirl sourdough bread.