Place both pumpkin halves flesh side down on a rimmed baking sheet and pour about a cup of water at the bottom.
Bake your pumpkin in a 375°F oven for about an hour, or until it's really soft and can its flesh and skin can very easily be pierced with the tip of a sharp knife.
Let the pumpkin cool until it can be safely handled, then scoop the flesh out with a large spoon and discard the skin.
Place the flesh into the bowl of your food processor(obviously you're gonna need to work in batches!) and process until your puree gets silky smooth.
Transfer your finished puree to several airtight containers or resealable plastic bags of the desired size and keep in the refrigerator for up to a week or freeze for up to several months.
If you're an expert in canning, you can even can these so the puree will last you throughout the year, until pumpkins are in season again.