Preheat oven to 350°F. Spread the sunflower seeds out on a rimmed baking sheet. Roast in the oven for 12 to 15 minutes, stirring the seeds at least once during baking, to ensure even roasting.
When the sunflower seeds are fragrant and golden brown, remove the pan from the oven. Let the seeds cool 10 to 15 minutes. Carefully pour them into the bowl of a food processor.
Process the seeds for about 30 seconds, until the seeds have broken down into a rough meal. Add the salt and process again.
Continue to process in 20-30 second stints, stopping the motor and removing the lid after each stint to break up any clumps and scrape down the sides of the processor.
The sunflower butter will look like wet sand and then will start to roll around the processor in one or two large clumps.
At this point, stream in 1 tablespoon of the sunflower oil and continue to process. If it doesn’t look liquidy and buttery within 15 to 20 seconds, add a second tablespoon. Should it still resist, go with one more.
When the butter pools in the food processor bowl and looks quite spreadable, it is done.
Scrape the finished butter into a jar or container. It will keep 2-3 weeks at room temperature. For longer storage, refrigerate.
To make the sunflower seed butter into Cinnamon Vanilla Butter, add 1-2 teaspoons of cinnamon, 2 teaspoons vanilla bean paste, and 2 tablespoons sugar with the salt.