Combine broccoli florets, parmesan cheese, dried cranberries, bacon , sunflower seeds, and onion in a large bowl.
In a separate bowl, whisk together mayo, sour cream, lemon juice, sugar, salt, and pepper until well combined.
Pour dressing over the broccoli salad and toss till evenly coated.
Broccoli salad may be served immediately, but for the best flavor refrigerate for at least one hour before serving.