Preheat oven to 375°F. Set aside a lined baking sheet for the cookies.
Blot the pumpkin puree with a paper towel to remove some of the moisture (otherwise your cookies will be too soft).
Mix together pumpkin spice/sugar coating in a shallow bowl and set aside.
Cream together coconut oil and sugar. Add pumpkin puree and vanilla extract and briefly combine.
In a separate bowl, mix together flour, cream of tartar, baking soda, and salt. Add to wet ingredients and mix until a cookie dough forms. Add a splash of plant milk if the batter is too dry.
Scoop cookie dough into balls (about 1 tbsp in size) and roll in cinnamon sugar mixture. Place on baking sheet and flatten slightly into discs.
Bake 10 minutes, until lightly golden and firm around the edges. (The center will still be soft but will firm up as it cools.) Leave on the baking sheet for 2-3 minutes, then transfer to a cooling rack. Let cookies cool completely before eating for best results. Store leftovers in an air-tight container at room temperature, or freeze to be eaten in the future.