1. Brown the butter: melt butter in a light-colored saucepan over medium heat until foamy and golden brown, then let cool for 15 minutes.

2. Whisk cooled brown butter with brown sugar and granulated sugar until creamy.

3. Add pumpkin puree, vanilla extract, and egg yolk; mix until smooth.

4. In a separate bowl, whisk flour, baking soda, cream of tartar, cinnamon, nutmeg, and salt.

5. Gradually add dry ingredients to wet ingredients, stirring until a soft dough forms. Do not overmix.

6. Chill dough for 30–45 minutes.

7. Preheat oven to 350°F (175°C). Scoop tablespoon-sized dough balls, roll in cinnamon-sugar coating, place 2 inches apart on a lined baking sheet, and bake 10–12 minutes until edges are set. Let rest 5 minutes before cooling on a wire rack.