Mayo chicken

Grease an oven-proof dish with butter, put onion slices on the bottom of the dish, arrange chicken breasts on the onions, season with salt and pepper, pour mayonnaise on top and cover with cheese slices. Cover the dish and bake for 20 mins at 220°C, uncover and bake until the cheese is golden and bubbling and the chicken breasts are cooked through. Serve with potatoes or chips.