Combine dry ingredients: Whisk flour, cream of tartar, baking soda, cinnamon, pumpkin pie spice, and salt together.
Cream butter and sugars: Beat softened butter with both sugars until light and fluffy for three minutes.
Add wet ingredients: Mix in egg, pumpkin puree, and vanilla until smooth and well combined throughout.
Mix dough: Gradually add dry ingredients to the wet mixture and stir until just combined completely.
Chill dough: Refrigerate for 30 minutes so the dough firms up and becomes easier to handle nicely.
Prepare coating: Mix cinnamon and sugar in a small bowl until evenly combined and ready.
Shape cookies: Scoop dough, roll into balls, and coat generously in the cinnamon sugar mixture.
Bake cookies: Place on parchment-lined sheets and bake at 350°F for 10-12 minutes until done.
Cool cookies: Let rest on baking sheet 5 minutes before transferring to cooling rack carefully.