Preheat oven to 400 degrees.
Drizzle the cauliflower and onion generously with olive oil and season with salt and pepper. Place into a preheated oven for 15 minutes.
Cook bacon lightly and take off heat when golden. When cooled, chop into smaller pieces.
When the cauliflower and onions have roasted for 15 minutes, remove from the oven and add Castello Dill Havarti Cheese. Place back into the oven for an additional 10 minutes. The cheese will melt on top of the cauliflower and fall to the sides.
Once cheese has melted, top with bacon and roast for 5 minutes. Garnish with parsley. Serve immediately.