Brown the butter: In a small saucepan, melt the butter over medium heat, stirring frequently. Continue to cook until it begins to foam and turns golden brown with a nutty aroma (about 5–7 minutes). Immediately transfer to a mixing bowl and let cool for 10–15 minutes.

Mix wet ingredients: To the cooled brown butter, add granulated sugar, brown sugar, pumpkin purée, and vanilla extract. Whisk until smooth.

Add dry ingredients: In a separate bowl, whisk together flour, cinnamon, pumpkin pie spice, baking soda, baking powder, cream of tartar, and salt. Gradually mix into the wet ingredients until just combined. Chill dough for 30 minutes.

Preheat oven: While the dough chills, preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.

Make the rolling mixture: In a small bowl, stir together sugar, cinnamon, and pumpkin pie spice for rolling.

Shape & roll: Scoop out about 1 tablespoon of dough and roll into balls. Roll each dough ball in the cinnamon-sugar mixture and place on the prepared baking sheet, spacing about 2 inches apart.

Bake: Bake for 10–12 minutes, or until edges are set but centers still look soft. Let cool on the baking sheet for 5 minutes, then transfer to a wire rack.