In a medium bowl, whisk the flour, cream of tartar, pumpkin pie spice, salt, baking powder, and baking soda together; set aside.
In a large mixing bowl using an electric mixer, cream together the butter, granulated sugar, and brown sugar for 1 to 2 minutes or until well combined.
Mix in the egg yolk followed by the vanilla and the pumpkin puree. Stop to scrape down the sides of the bowl as needed.
Add the dry ingredients and mix until just combined.
Cover the bowl with plastic wrap and refrigerate for 30 minutes. Meanwhile, preheat the oven to 350°F. Line two large baking sheets with parchment paper.
Using a 1.5 tablespoon scoop, scoop the dough and roll it into balls. Place each dough ball about 2 inches apart on the prepared baking sheets.
Mix the sugar and cinnamon together for the coating. Roll each dough ball generously in the coating and return to the baking sheets.
Bake for 11-12 minutes until the edges are set. The centers will still look soft. Remove from the oven and gently press the cookies down with the back of a spoon. They'll be puffy.
Leave on the cookie sheets for 10 minutes. Then transfer to a wire rack to cool completely.
Notes
Cookies will keep for up to 1 week stored in an airtight container.
Pumpkin: Be sure to use pumpkin puree and not pumpkin pie filling.
Make ahead tip
Cookie dough can be rolled and frozen for up to three months. Coat with cinnamon sugar just before baking and add an additional 1-2 minutes to the bake time.
Baked cookies will freeze well for up to three months. Thaw to room temperature just before serving.