Preheat your oven to 350F and spread the sunflower seeds into a thin layer on a large rimmed baking sheet. (I only have small rimmed baking sheets, so I had to use two pans.) Toast them until the seeds start to turn lightly golden and have a nutty aroma, about 20 to 25 minutes. You'll want to watch and stir the seeds every 10 minutes or so while they're toasting to make sure they don't burn.
Once the seeds are toasted, pour them into a food processor fitted with an "S" blade and start processing them. Just like making almond butter, you'll need a bit of patience during this part. First, the sunflower seeds will be ground into a fine meal, and in about 5 to 6 more minutes, it should start to form a sticky ball.
After the ball stage, it took another 5 minutes or so for the butter to reach a creamy consistency. Once the butter is smooth, you can add the coconut sugar and salt, to taste, and keep processing for a couple more minutes to incorporate it evenly.
Transfer the butter to a glass jar with an airtight lid and store it in the fridge for up to a month. (It might last longer than that, but we usually use it all by then!)