Chewy Pumpkin Snickerdoodle Cookies

Preheat oven to 350 degrees Fahrenheit and line three baking sheets with parchment paper.
In a large bowl, cream butter, sugar, and brown sugar together for with an electric mixer on medium speed for about 2 minutes, until light and fluffy.
1/2 cup unsalted butter, 1/2 cup sugar, 1/4 cup brown sugar
Add the egg yolk, vanilla extract, and pumpkin puree for continue mixing until smooth, about 1 minute.
1 egg yolk, 1 tsp vanilla extract, 1/4 cup pumpkin puree
In a separate bowl, whisk the flour, baking soda, cream of tartar, pumpkin pie spice, cinnamon, and sea salt together.
1 1/4 cup flour, 1/2 tsp baking soda, 1 tsp cream of tartar, 1 tsp pumpkin pie spice, 1/2 tsp cinnamon, 1/2 tsp sea salt
Add flour mixture to the wet ingredients, mixing with a wooden spoon or a rubber spatula until just combined. Try not to overmix the dough or the cookies will be stiff.
Using a 2 TBS cookie scoop, scoop dough, roll into a ball with your hands, and generously roll in cinnamon sugar mixture. Place coated cookies on a lined baking sheet 2 inches apart.
Bake cookies at 350 degrees Fahrenheit for 9-10 minutes, rotating the pan halfway through. Cookies will be slightly puffy and cracked on the top. Don't overbake them or they will be dry.
Let cookies cool on the baking sheet until they are sturdy enough to transfer to a wire rack to cool completely.
Store cookies in an airtight container for 3-5 days or freeze for up to 3 months.