Preheat the oven to 350 degrees Fahrenheit and line a large baking sheet or two small baking sheets with parchment paper.
Transfer the butter and sugars to the bowl of a stand mixer fitted with a paddle attachment. Beat on medium-high speed until well combined and fluffy. Use a rubber spatula to scrape the sides of the bowl and add the vanilla extract, pumpkin puree, and egg yolk. Beat until the wet ingredients are well combined. Again, scrape the sides of the bowl.
In a separate bowl, stir together the flour, cream of tartar, baking soda, pumpkin pie spice, ground cinnamon, and sea salt.
Transfer the dry ingredients to the stand mixer with the wet ingredients and beat on medium speed until the dough comes together. If the dough appears too sticky, refrigerate it for 20 minutes. Otherwise, go straight to baking!
In a small bowl, combine the granulated sugar and cinnamon for rolling the cookie dough balls.
Use a small cookie scoop to scoop out equal portions of dough and roll them into balls.
Press each dough ball into the cinnamon sugar mixture to coat the full ball.
Transfer the dough balls to the prepared baking sheet, leaving a little space between. The cookies won’t spread much during the baking process. Use the back of a spoon to press down on each dough ball in order to flatten them out. This ensures the cookies bake to the right shape and thickness, as they won’t spread otherwise.
Bake on the center rack of the preheated oven for 10-12 minutes, or until the edges are slightly golden brown.
Allow the cookies to cool for at least 10 minutes on the baking sheet before moving them. During this time, you can sprinkle the cookies with the rest of the cinnamon-sugar mixture if you’d like to get some extra sweetness and texture.