Combine the broccoli florets, cheese, cranberries, bacon, onion, and sunflower seeds in a large bowl. Set aside.
In a small bowl, whisk together mayo, sugar, vinegar, salt, and pepper until well combined.
Pour the dressing over the broccoli mixture and toss together until well combined.
Place in the refrigerator for 2 hours and toss together once more before serving.
Notes
Regular shredded cheese is better for this recipe than the finely shredded variety.
Some people prefer to blanch their broccoli first. I never do. If you want to blanch your broccoli, cook it in boiling water for one minute and then remove it to a strainer/colander and rinse it with cold water until it cools completely. Dry it well before using it in the recipe as directed.