Preheat oven to 350°F. Line two baking sheets with parchment paper.
Whisk flour, cream of tartar, baking soda, salt, cinnamon, and pumpkin spice in a bowl.
Beat softened butter, granulated sugar, and brown sugar until light and creamy, about 2 minutes.
Mix in pumpkin puree and vanilla until smooth. Scrape the bowl.
Add dry ingredients to wet on low speed. Mix just until combined; dough will be soft.
Chill dough 20–30 minutes to firm slightly for easier rolling.
Stir coating: granulated sugar, cinnamon, and pumpkin spice in a shallow bowl.
Scoop dough into 1.5-tablespoon portions. Roll into balls, then coat generously in the spiced sugar.
Arrange on sheets, spacing 2 inches apart. Gently flatten tops slightly with your fingers.
Bake 10–12 minutes, until set at edges and soft in centers.
Cool on the sheet 5 minutes, then move to a rack to finish cooling.