Pierce the pumpkin with a knife in several places to allow the steam to escape.
Put the pumkin in a baking dish. Put in the oven and bake for 1 hour.
Remove baked pumpkin from the oven and cut in half. Scoop out the seeds and discard or reserve for another use. With a spoon, separate the pumpkin flesh from the skin.
Put cooked pumpkin flesh in a food processor or blender and process until it's smooth and turns into a pumpkin puree.
Notes
If you are an Instant Pot owner, you can cook pumpkin in the Instant Pot instead of the oven and make pumpkin puree with it!