Step 1Heat the oven to 350 degrees. Line a rimmed baking sheet with foil.
Step 2Split the pumpkin from stem to blossom end. Scoop out and discard all the seeds and fibrous strings. Place the halves cut side up on the baking sheet and drizzle with the olive oil, using your fingers rub it all over the exposed flesh. Season the pumpkin liberally with salt and pepper. Bake until the pumpkin is very tender and lightly caramelized at the edges, about 2 hours.
Step 3Remove the sheet from the oven and let the pumpkin cool. While it is still slightly warm, scoop the pumpkin flesh from the skins and either mash it or puree it in a food processor. Use immediately or store in an airtight container in the refrigerator for up to 3 days or freezer for up to 2 months; thaw before using.