Cook bacon in a large skillet over medium heat until deeply crispy, about 8–10 minutes. Transfer to a paper towel-lined plate and let cool completely, then crumble into chunky pieces.

In the same skillet (wiped clean) or a separate dry pan, toast the sunflower seeds over medium heat for 2–3 minutes, stirring frequently, until golden and fragrant. Remove from heat and let cool.

In a medium bowl, whisk together the mayonnaise, apple cider vinegar, sugar, Dijon mustard, salt, and black pepper until smooth and fully combined. Taste and adjust sweetness or acidity as needed. Set aside.

Cut the broccoli into small, bite-sized florets. Place the sliced red onion in a bowl of ice water and let soak for 10 minutes to mellow the sharp bite, then drain and pat dry.

In a large mixing bowl, combine the broccoli florets, crumbled bacon, cheddar cubes, toasted sunflower seeds, drained red onion, and raisins.

Pour the dressing over the salad and toss thoroughly until every floret is well coated. Taste and season with additional salt and pepper if needed.

Cover and refrigerate for at least 1 hour before serving to allow the flavors to meld. Add an extra scatter of bacon and sunflower seeds on top just before serving for presentation and crunch.