Fill a large steamer pot with 1-2 inches of water and bring to a boil.
Meanwhile, slice off the stem of the pumpkin, then cut in half and scoop out the seeds. Discard or use the seeds in another recipe.
Slice the pumpkin into evenly sized pieces, about 1 cm wide. Place in the steamer basket on top of the pot, cover, and let steam for 20 minutes. Depending on the size of your pumpkin and steamer basket, you may have to steam in two batches.
When the timer is up, the pumpkin flesh should be evenly colored and easily pierced with a fork. Wait for it to cool slightly so it’s easy to handle, then peel or slice off the skin and discard.
Place the pumpkin flesh in a bullet blender and blend until puree is formed, which should only take a few seconds.
If not using right away, store in an airtight container in the fridge. Should last up to 5 days.