In a large mixing bowl, combine the broccoli florets, cheddar cheese, cranberries, bacon, sunflower seeds, and diced red onion.
In a separate small bowl, whisk together the mayonnaise, sour cream, white wine vinegar, sugar, salt, and pepper until smooth and creamy.
Pour the dressing over the broccoli mixture and toss thoroughly to coat all ingredients evenly.
For optimal flavor, refrigerate the salad for at least one hour before serving. Toss the salad again prior to serving.
Store in the refrigerator if not serving immediately.