Cut pumpkin in half vertically. Scoop out the seeds and set aside. Rub the cut edges of the pumpkin with a small amount of olive oil or water, then set cut-side down on a rimmed baking sheet.
Roast for 35-60 minutes, depending on the size of the pumpkin, until soft. Let cool.
Scoop out pumpkin from the skin and transfer to a food processor. Puree until completely smooth.
Transfer to an airtight container and store in the refrigerator until ready to use, or freeze for longer storage.