Starting with a clean pumpkin, cut a circle around the stem and remove. Using a spoon, scrape out seeds and stringy flesh from inside the pumpkin and discard.
Add 1 cup of water to instant pot. Place pumpkin into instant pot (you can use the rack or not, it doesn't matter). Close lid and seal pressure valve. Cook on manual/high pressure.
Scrape the pumpkin flesh away from the skin, and place into a blender or food processor, or back into the instant pot and use a hand blender. Blend until completely pureed.