Melt unsalted butter in a medium saucepan over medium heat, swirling constantly. Once foaming subsides, cook for 3-4 minutes until nutty, amber brown, with toasted specks. Pour into a bowl to cool.

Spread pumpkin puree over 4 layers of paper towels and press gently with another paper towel to blot out excess moisture (crucial for chewy cookies!).

In a large bowl, whisk cooled browned butter, dark brown sugar, and granulated sugar for 1 minute until smooth. Whisk in blotted pumpkin puree, egg yolk, and vanilla extract until glossy.

Whisk flour, cream of tartar, baking soda, pumpkin pie spice, and salt in a separate bowl. Fold dry ingredients into wet ingredients with a rubber spatula just until combined.

Cover dough and chill in the refrigerator for 30 minutes to firm up and allow butter flavors to deepen.

Preheat oven to 350°F (175°C) and line two baking sheets with parchment paper. Whisk granulated sugar and cinnamon in a small shallow bowl.

Scoop 1.5-tablespoon balls of dough, roll smoothly in palms, then toss generously in cinnamon sugar coating. Place 2 inches apart on baking sheets.

Bake for 9-11 minutes until edges are set and center is puffy and cracked. Immediately tap the baking sheet firmly on the counter 2-3 times to create crinkles, then let cool 10 minutes on sheet before transferring to a wire rack.