Combine all of the dressing ingredients in a small bowl and stir until smooth.
Add the broccoli to a large mixing bowl. Pour the ¾ of the dressing over top and stir until the broccoli is well coated. If the broccoli seems too dry add more of the dressing until it is all coated.
Add the cheese, cranberries, bacon, sunflower seeds, and onion then stir gently until just combined. Cover and refrigerate for 1 hour, up to overnight. Stir again just before serving.