Spread 1/2 cup of pure pumpkin puree onto a plate lined with 4 layers of paper towels. Press firmly with another 2 layers of paper towels on top to absorb excess water. Repeat twice until you have about 1/3 cup of thick, concentrated pumpkin paste. This single step ensures cookies are chewy instead of cakey!

In a small bowl, whisk together granulated sugar, cinnamon, and pumpkin pie spice for the coating. Set aside.

In a large bowl, whisk melted butter, brown sugar, and granulated sugar until smooth. Whisk in the blotted pumpkin puree, egg yolk, and vanilla extract until glossy and combined.

In a separate bowl, whisk flour, cream of tartar, baking soda, cinnamon, nutmeg, and salt. Fold the dry ingredients into the wet batter with a spatula until a soft dough forms. Chill dough in the refrigerator for 30 minutes.

Preheat oven to 350°F (175°C). Line two large baking sheets with parchment paper.

Scoop 1.5-tablespoon portions of chilled dough and roll into smooth balls. Roll each ball generously in the spiced cinnamon sugar coating, covering completely.

Place balls 2 inches apart on prepared baking sheets. Bake at 350°F (175°C) for 10 to 11 minutes until edges are set and tops are puffed and crinkled. The centers should still look slightly soft.

Remove from oven and let rest on the hot baking sheet for 5 minutes (they will settle into chewy perfection), then transfer to a wire cooling rack. Serve warm!