Place a large skillet over medium heat and add the bacon slices in a single layer. Cook for 8 to 10 minutes, flipping occasionally, until deeply browned and crisp on both sides.
Transfer the cooked bacon to a paper towel lined plate to drain and cool. Once cool enough to handle, crumble or chop the bacon into small bite sized pieces and set aside.
Rinse the broccoli florets under cold water and pat them completely dry with a clean towel. Using a sharp knife, cut the florets down into small, bite sized pieces, about the size of a grape.
Finely dice the red onion into small pieces so it distributes evenly through every bite. Set the chopped broccoli and onion aside in a large mixing bowl.
In a small bowl, add the mayonnaise, apple cider vinegar, and granulated sugar. Whisk the mixture together until it is completely smooth and the sugar has dissolved.
Season the dressing with a pinch of salt and black pepper, then whisk once more to combine. Taste and adjust, adding a touch more sugar if you prefer a sweeter dressing or more vinegar for extra tang.
Add the crumbled bacon, shredded cheddar cheese, sunflower seeds, and dried cranberries to the bowl with the broccoli and onion. Gently toss all of the ingredients together with a large spoon until evenly distributed.
Pour the prepared dressing over the top of the salad. Fold everything together gently, making sure every piece of broccoli gets coated in dressing.
Cover the bowl tightly with plastic wrap or transfer the salad to an airtight container. Refrigerate for at least 1 hour, though 3 to 4 hours or overnight will give you the best flavor.
Give the salad a good stir right before serving, since the dressing tends to settle at the bottom. Serve cold, straight from the fridge, as a side dish or light lunch on its own.