Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, baking soda, cream of tartar, cinnamon, nutmeg, and salt. Set aside.
In a large bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy.
Add the pumpkin puree, vanilla extract, and egg, and mix until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
In a small bowl, mix the additional granulated sugar and cinnamon for rolling.
Scoop the dough into balls and roll them in the cinnamon-sugar mixture.
Place the dough balls on the prepared baking sheet and bake for 8-10 minutes, or until lightly golden.
Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.