Preheat your oven to 350°F (180°C) and line two baking trays with parchment paper.

Melt 1 cup of unsalted butter in a stainless steel pan over medium heat until golden brown and nutty, then allow to cool slightly.

Pour the browned butter into a glass measuring cup and chill in the fridge for 45-60 minutes until it reaches 70-75°F (21-24°C).

Press excess moisture from the pumpkin puree using paper towels until it feels dry.

In a bowl, whisk the dark brown sugar and granulated sugar into the cooled butter until it resembles wet sand.

Add the egg yolks and vanilla extract, whisking until combined, then stir in the prepared pumpkin puree.

In another bowl, whisk flour, pumpkin spice, baking soda, cream of tartar, and salt. Gradually fold this dry mixture into the wet ingredients without overmixing.

Chill the dough in the refrigerator for at least 5 minutes.

Combine the cinnamon and sugar in a small bowl for rolling.

Scoop the dough into 3-tablespoon-sized balls, roll each in the cinnamon sugar, and place on the baking sheets spaced 2-3 inches apart.

Bake for 10-12 minutes until edges are golden and middle is slightly underbaked. Cool on a wire rack before serving.