Start by melting the unsalted butter in a saucepan over medium heat. Stir occasionally until it turns golden brown and emits a nutty aroma—this takes about 5-7 minutes. Once browned, remove from heat and allow to cool slightly.

In a large mixing bowl, combine the browned butter, pumpkin puree, regular sugar, and brown sugar until well blended. Add the eggs one at a time, mixing well after each addition, followed by the vanilla extract.

In a separate bowl, whisk together the all-purpose flour, baking soda, cream of tartar, ground cinnamon, ground nutmeg, and salt. Gradually add the dry ingredients to the wet mixture, stirring until just combined.

Cover the cookie dough with plastic wrap and refrigerate for at least 30 minutes.

Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.

In a small bowl, mix together the sugar and cinnamon for rolling. Scoop out tablespoon-sized portions of the chilled dough and roll them into balls. Roll each ball in the cinnamon-sugar mix.

Space the cookie balls on the prepared baking sheet and bake for 10 to 12 minutes, or until the edges are lightly golden but the center is still soft. Allow to cool for a few minutes before transferring to a wire rack.