Prepare the Dough:
Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a large mixing bowl, cream together the softened butter, pumpkin puree, granulated sugar, and dark brown sugar until smooth and fluffy. Add the egg yolks, one at a time, mixing well after each addition. Stir in the vanilla extract.

Combine Dry Ingredients:
In a separate bowl, whisk together the all-purpose flour, pumpkin spice, baking soda, cream of tartar, and kosher salt.

Mix Wet and Dry Ingredients:
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix. The dough should be soft and slightly sticky.

Chill the Dough (optional):
For best results, chill the dough in the refrigerator for at least 30 minutes. This will help the cookies hold their shape and prevent them from spreading too much during baking.

Prepare the Cinnamon-Sugar Coating:
In a small bowl, combine the granulated sugar and ground cinnamon. Mix until well combined.

Form the Cookies:
Scoop tablespoon-sized portions of dough and roll them into balls. Roll each ball in the cinnamon-sugar mixture, ensuring it’s fully coated.

Bake the Cookies:
Place the dough balls onto the prepared baking sheets, spacing them about 2 inches apart. Bake for 10-12 minutes, or until the cookies are set around the edges but still soft in the center. They will firm up as they cool.

Cool and Serve:
Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely. Enjoy with a glass of milk or as a festive snack!