Easy as pie, and almost as delicious.
Preheat oven to 400 degrees.
Remove the stem from your pumpkin, cut in half and place facedown on a baking sheet. Leave the seeds intact; it's easier to remove them after roasting.
Roast for 40 - 60 minutes. Insert a knife into the flesh and continue roasting if there is any resistance. The longer you roast the pumpkin, the darker and sweeter the flesh will be, so don't rush it.
Remove the tray from the oven. Carefully flip the halves over so that the seed sides are facing up and let cool for at least 10 minutes.
Once cool enough to handle, scoop out the seeds and peel off the skin.
Chop roughly and add to a food processor or blender. Blend until smooth.
Seal in a jar or air tight container for up to one week.