In a medium bowl, whisk together flour, cream of tartar, baking soda, salt, and pumpkin pie spice.2 3/4 cups all-purpose flour,2 teaspoons cream of tartar,1 teaspoon baking soda,1/2 teaspoon salt,1 teaspoon pumpkin pie spice.
In a large bowl, cream together butter and 1 1/3 cups sugar until light and fluffy.1 cup unsalted butter,1 1/3 cups granulated sugar.
Beat in the egg, pumpkin puree, and vanilla extract until well combined.1 large egg.3/4 cup pumpkin puree,2 teaspoons vanilla extract.
Gradually mix in the dry ingredients until just combined.
Cover the dough and refrigerate for at least 30 minutes.
Preheat oven to 350°F. Line baking sheets with parchment paper.
In a small bowl, mix 1/4 cup sugar and cinnamon for rolling.1/4 cup granulated white sugar,2 teaspoons ground cinnamon.
Roll chilled dough into 1-inch balls, then roll in the cinnamon-sugar mixture.
Place on prepared baking sheets, about 2 inches apart.
Bake for 10-12 minutes, until edges are lightly golden.
Let cool on the baking sheet for 5 minutes before transferring to a wire rack.
Notes
Pro Tip: For an extra pumpkin flavor, increase the pumpkin puree to 1 cup and reduce the flour to 2 1/2 cups. This adjustment will give you a stronger pumpkin taste and softer texture.