Preheat the oven to 400°F. Line a baking sheet with parchment paper or a silicone baking mat. With a large knife, cut the pumpkin in half then scoop out the seeds (see notes).
Place the pumpkin halves cut side down on the prepared baking sheet.
Bake in the preheated oven for 35-45 minutes, or until the flesh is tender and the pumpkin skin is puckered and brown.
Remove from the oven and allow to cool until it's just cool enough to handle. Peel the skin from the pumpkin halves and place the flesh in the bowl of a food processor.
Process until smooth. If the puree is too watery, strain it using cheesecloth or a Greek yogurt strainer.
Store in an airtight container in the fridge for up to a week. For longer storage, portion the puree into freezer bags, flatten them, and freeze for up to a year.
Notes
You want to avoid the big pumpkins used for carving jack-o-lanterns. Their flesh is too watery and fibrous for this recipe. Look for small sugar pumpkins (sometimes called baking pumpkins or pie pumpkins). Their flesh is dense and sweet!
Save those pumpkin seeds! One of the best parts of making homemade pumpkin puree is that you get to roast pumpkin seeds. They make a fun and delicious snack.