1) Preheat oven to temperature of 380 degrees.
2) In a saucepan, place the peeled whole onions. Cover with cold water and bring to a boil gently and slowly. Drain.
3) In a casserole or a baking dish, put the onions along with butter and water or stock.
4) Cover the dish with a lid and place it in the center of the preheated oven. Cook for 1 hour.
5) Take the lid off, drain the onions and sprinkle with salt.
6) Serve right away.