Spread the pumpkin purée across a paper plate lined with 4 layers of paper towels. Press firmly with 3 additional paper towels on top to absorb excess moisture until the purée compresses from 1/2 cup down to roughly 1/3 cup. This crucial step guarantees chewy cookies rather than cakey puffs!

In a large mixing bowl, whisk together the melted butter, granulated sugar, and brown sugar until glossy and smooth.

Whisk in the blotted pumpkin purée, egg yolk, and pure vanilla extract until completely emulsion-smooth and creamy.

In a separate medium bowl, whisk together the all-purpose flour, cream of tartar, baking soda, fine sea salt, and pumpkin pie spice.

Pour the dry ingredients into the wet mixture. Fold gently with a rubber spatula just until no dry flour streaks remain. The dough will be soft and fragrant.

Cover the bowl tightly with plastic wrap and chill in the refrigerator for 30 to 45 minutes to firm up the dough and allow the spices to blossom.

Preheat your oven to 350°F (175°C). Line two large baking sheets with parchment paper. In a small shallow bowl, whisk together 1/4 cup granulated sugar and 1.5 teaspoons ground cinnamon.

Using a medium cookie scoop (about 1.5 tablespoons of dough), scoop and roll dough into smooth round balls between your palms.

Roll each dough ball generously in the cinnamon sugar mixture until fully coated in sparkling crystals. Place 2 inches apart on the prepared baking sheets.

Bake at 350°F (175°C) for 10 to 11 minutes. The cookies will puff, crinkle across the top, and set around the edges while remaining tender in the center. Do not overbake!

Remove from oven and gently tap the baking sheet on the counter once to encourage gorgeous crinkles. Let cool on the baking sheet for 5 minutes, then transfer to a wire cooling rack. Enjoy warm with a glass of milk or chai latte!