Melt the butter in a light-colored saucepan over medium heat.
¾ cup unsalted butter
Stir constantly for 5 to 7 minutes, until it foams, quiets down, and turns golden with brown flecks at the bottom. Scrape those flecks in, they carry the flavor.
Pour into a large bowl and refrigerate 20 to 30 minutes, stirring now and then, until it has the texture of soft face cream.
Blot the pumpkin puree
Measure ½ cup (120g) pumpkin puree and spread it across a double layer of paper towels.
⅓ cup blotted pumpkin puree
Fold the towel over and press gently. Repeat with fresh towels until the puree looks matte and feels like a thick paste.
Re-measure. You want ⅓ cup, 75 to 80g. Do not take it past that.
Mix the wet ingredients
Whisk both sugars into the cooled brown butter until smooth.
⅔ cup dark brown sugar, ⅓ cup granulated sugar
Mix in the egg yolk, blotted pumpkin puree, and vanilla until well combined.
1 large egg yolk, 1 ½ tsp vanilla extract
Combine dry ingredients
In a separate bowl, whisk together the flour, baking soda, cream of tartar, salt, pumpkin pie spice, and cinnamon.
1 ½ cups all-purpose flour, ½ tsp baking soda, ½ tsp cream of tartar, ½ tsp salt, 2 tsp pumpkin pie spice, ½ tsp ground cinnamon
Make the dough
Gently fold the dry ingredients into the wet mixture until just combined.
Preheat to 350°F and line baking sheets with parchment paper. Scoop 2 tbsp mounds of dough or about 41 grams of dough. Roll each mound lightly in the cinnamon-sugar topping.
3 tbsp granulated sugar, 1 tsp ground cinnamon
Place 3 inches apart on the baking sheet.
Leave them on the hot pan for 5 minutes, then transfer to a wire rack.
Leave them on the hot pan for 5 minutes, then transfer to a wire rack.
Notes
Pumpkin blotting reference. Start with ½ cup (120g) of puree. Blot until it weighs 75 to 80g, which is about ⅓ cup. Over 80g and the cookies bake cakey. Under 75g and they turn crumbly. If you only have cups, blot until the puree holds its shape on the sCool down the brown butter. If your brown butter is not chilled enough, you risk having cookies that spread too much. Bake one test cookie if you are unsure. If it spread to your liking, perfect, bake the rest of the cookie dough. If it spreads too much, chill the cookie dough in the fridge for 15-20 minutes then bake!