Measure the 1/3 cup (80g) pumpkin puree, then spread it over a few layers of paper towels. Gently blot with additional paper towels to remove as much excess moisture as possible. Set aside.
Preheat the oven to 350°F. Line baking sheets with parchment paper.
In a medium bowl, whisk together the 2 1/2 cups (312g) all-purpose flour, 1 teaspoon cream of tartar, 3/4 teaspoon baking soda, 1/2 teaspoon salt, 1 1/2 teaspoons ground cinnamon, and 1 teaspoon pumpkin pie spice. Set aside.
In a large mixing bowl, beat the 3/4 cup (170g) unsalted butter, softened to room temperature, 2/3 cup (135g) packed light brown sugar, and 1/2 cup (100g) granulated sugar for 2–3 minutes, until light and fluffy.
Beat in the 1 large egg yolk and 2 teaspoons vanilla extract. Add the blotted pumpkin and mix until well combined.
Gradually add the dry ingredients and mix just until combined. Don’t worry if the dough looks dry. Once you add the flour, it may seem like there’s too much and the dough won’t come together. Keep mixing! If needed, turn off the mixer and use your hands to work in the remaining flour. It will come together into a soft cookie dough.
In a small bowl, stir together the 1/3 cup (67g) granulated sugar, 2 teaspoons ground cinnamon, and 1/2 teaspoon pumpkin pie spice.
Use a medium cookie scoop (#50, about 1 1/2 tablespoons) to portion the dough. Roll into balls, then generously coat each ball in the cinnamon-sugar mixture. Place about 2 inches apart on the prepared baking sheets.
Bake for 10–12 minutes, or until the edges are set and the centers still look slightly soft. Avoid overbaking for the best soft and chewy texture.
Let the cookies cool on the baking sheet for about 10 minutes, then transfer to a wire rack to cool completely.