Slice a baking pumpkin in half and remove the seeds and pulp. Lay the two halves face down on a rimmed baking sheet. Bake them at 400˚F for 40-45 minutes, until tender. Allow the pumpkin to cool. Scoop out the pumpkin flesh and puree it in a blender or food processor. Store in the fridge for up to 1 week or the freezer for up to 3 months.