Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.

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

In a medium bowl, whisk together the flour, baking soda, cream of tartar, cinnamon, and salt. Set aside.

In a large bowl, cream together the softened butter, granulated sugar, and brown 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.

Using a cookie scoop, portion out the dough and roll each ball in the cinnamon sugar mixture.

Place the coated dough balls on the prepared baking sheet, spacing them about 2 inches apart.

Bake in the preheated oven for 10-12 minutes, or until the edges are set but the centers are still soft.

Remove from the oven and let cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.