Spread paper towels on a plate, scoop the pumpkin puree on top, cover with more paper towels, and press gently to soak up excess moisture. Let sit for 10 to 15 minutes.
Preheat the oven to 375°F (190°C) and line two large baking sheets with parchment paper or silicone baking mats.
In a medium bowl, whisk together the flour, cream of tartar, baking soda, salt, pumpkin pie spice, and 1/2 teaspoon ground cinnamon until evenly combined.
In a large bowl, beat the softened butter, 1/2 cup granulated sugar, and brown sugar with a hand mixer on medium speed for 1 to 2 minutes until light, fluffy, and pale.
Add the egg yolk and vanilla, beat for 30 seconds, then add the blotted pumpkin puree and mix until smooth and uniform in color.
Add the dry ingredients to the wet ingredients in two additions, mixing on low speed just until no dry streaks of flour remain. Do not overmix.
In a small bowl, stir together 1/4 cup granulated sugar and 1 1/2 teaspoons ground cinnamon until evenly combined.
Using a medium cookie scoop, portion the dough into balls about 2 tablespoons each. Roll each portion into a smooth ball, then roll in the cinnamon sugar mixture until fully coated.
Place coated dough balls on the prepared baking sheets about 2 inches apart. Bake one sheet at a time on the middle rack for 10 to 12 minutes, until edges are set and tops are puffed and slightly cracked.
Let the cookies cool on the hot pan for 5 minutes to finish setting, then transfer to a wire cooling rack to cool completely. Repeat with remaining dough using a cool baking sheet.