Step 1: Wash and thoroughly dry the broccoli and cauliflower. Cut them into small, bite-sized florets. Aim for pieces that are roughly the same size for even texture. Finely dice the red onion.
Step 2: In a skillet over medium heat, cook the bacon until it's perfectly crisp. Remove the bacon, place it on a paper towel-lined plate to drain excess fat, and once cooled, crumble it into small pieces.
Step 3: In a medium bowl, combine the mayonnaise, apple cider vinegar, sugar, and Dijon mustard (if using). Whisk until completely smooth and well combined. Taste and adjust seasonings – you might want a pinch more sugar or vinegar depending on your preference.
Step 4: In a large mixing bowl, add the chopped broccoli florets, cauliflower florets, crumbled bacon, red onion, and sunflower seeds.
Step 5: Pour the prepared dressing over the vegetable mixture. Using a large spoon or spatula, gently fold and toss until all the vegetables are evenly coated.
Step 6: Cover the bowl tightly with plastic wrap and refrigerate for at least 2 hours. This chilling time allows the flavors to meld together and the raw vegetables to slightly soften, enhancing the overall texture and taste. Overnight chilling is even better!
Step 7: Give the salad a final toss before serving. Season with salt and freshly ground black pepper to taste, if needed. Serve chilled as a delicious side dish.