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

In a medium saucepan, melt the unsalted butter over medium heat. Continue cooking until it turns golden brown, releasing a nutty aroma. Stir frequently to prevent burning. Once browned, remove from heat and let it cool slightly.

In a large mixing bowl, combine the brown butter, pumpkin puree, granulated sugar, and brown sugar. Mix until well combined.

Add in the egg and vanilla extract. Beat gently until the mixture is fully incorporated.

In another bowl, whisk together the flour, cream of tartar, baking soda, salt, cinnamon, and nutmeg.

Gradually add the dry ingredients to the pumpkin mixture, mixing until just combined. Do not overmix!

In a small bowl, combine the ¼ cup of sugar and 1 tablespoon of cinnamon for rolling.

Use a cookie scoop or tablespoon to drop dough balls into the cinnamon-sugar mixture, rolling them evenly to coat.

Place the cookie dough balls on the prepared baking sheet, leaving space between each one.

Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden.

Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.