Preheat the oven to 350 degrees F and prepare a baking sheet pan with parchment paper; set aside until ready to use.
In a medium bowl combine the flour, baking soda, cream of tartar, pumpkin pie spice and salt. Mix to combine; set aside.
In a large mixing bowl, combine the melted butter and light brown sugar and whisk until fully combined.
Add the egg yolks, pumpkin puree, and vanilla extract to the butter and sugar mixture and whisk until combined.
Add the dry ingredients to the pumpkin mixture and whisk until smooth.
Scoop the cookie batter into 1.5 ounce balls and place on a line the prepared baking sheet.
Roll each cookie dough ball into the cinnamon sugar mixture until all dough balls are fully coated.
Place the cookie dough balls back on the baking sheet, approximately two inches apart and gently press the cookie down just to remove the rounded part of top. (DO NOT flatten the cookie dough)
Bake the Pumpkin Snickerdoodle Cookies at 350 degrees F for 9 minutes.
Remove the sheet pan from the oven and allow the cookies to cool for 10 minutes.
Serve or store in an airtight container! Enjoy!