Preheat the oven to 350 degrees Fahrenheit.  Prepare cookie sheets by lining them with parchment or spraying them with non-stick spray; set aside. 

In the bowl of a stand mixer, combine the softened butter, brown sugar and sugar.  Cream until smooth. 

Add in the pumpkin puree, egg yolks, vanilla, pumpkin pie spice, baking soda, cream of tartar and salt.  Combine well.  

Mix in the flour - scraping the sides and mixing again.  The dough will be sticky.

In a small bowl, combine the sugar and cinnamon for rolling. 

Scoop out dough about the size of a golf ball and roll in the cinnamon/sugar mixture.  

Place on a cookie sheet, leaving plenty of space to spread.  

Bake in the preheated oven for 10-12 minutes or until the edges are set and slightly browned.  The center should still be puffy but will settle once cooled.  If you overbake the cookies, they will not have this soft, chewy center.  

Allow to cool on the baking sheet for about 5 minutes before removing to finish cooling on a wire rack.  Enjoy!