Pre-heat your oven to 300°F / 150°C.
Spread the pumpkin seeds out on a baking sheet and toast for about 15 minutes, stirring occasionally. Allow the seeds to cool slightly.
Transfer the pumpkin seeds into the bowl of a food processor.
Pulse it a few times, then start running continuously. You'll need to stop and scrape the sides and bottom every once in a while.
At around the 5 minute mark the seeds should have gone from crumbly into a bit of a paste.
Keep running and scraping until it loosens up and becomes a smooth butter. Depending on your pumpkin seeds and your food processor, this should take about 15-20 minutes.
Add the salt, 1 tsp at a time, and tasting between each addition.
Scrape the pumpkin-seed butter into a clean jar.
