Preheat the oven to 160°C (320°F) and roast the whole onion in the skin for approx. 45 minutes. Flavour the mince with pepper, make four equal balls and flatten into burgers. Grill in a grill pan, on the barbecue, or fry in a frying pan until they are almost done.
Place a slice of cheddar on the burger during the last minutes so they melt slightly. Heat the rolls in the oven and cut them open. Peal the onion and cut into rings. Be careful, these may be hot inside. Fill the rolls with rinsed and dried lettuce, tomato, the burger, onion rings, and pickle.
Serve with freshly made salad and sauce to taste.