Preheat the oven to 350°F (175°C). In a mixing bowl, whisk together the flour, baking soda, cream of tartar, cinnamon, nutmeg, and salt.

In another bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy. Add the pumpkin puree, egg, and vanilla extract, mixing until well combined.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

In a small bowl, mix together the granulated sugar and cinnamon for the coating.

Using a cookie scoop, portion out the dough and roll each ball in the cinnamon sugar mixture. Place them on a baking sheet lined with parchment paper, spacing them about 2 inches apart.

Bake for 10-12 minutes, or until the edges are set and the tops are slightly cracked. Allow to cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.