In a large pot, place the beans and water and bring to a boil. Cover, reduce to a simmer and cook 1 hour, or until tender and creamy in the centers. Crush the beans in their liquid with a potato masher or the back of a wooden spoon. In a large saucepan, heat the lard or other fat over medium heat. Saute the onions with the salt until golden, about 20 minutes. Add the beans and liquid and continue cooking over medium heat, stirring frequently, until the liquid evaporates and the beans form a creamy mass that pulls away from the bottom and sides of the pan, about 15 minutes. Serve immediately. Refried beans can be kept in the refrigerator 3 or 4 days and reheated in a covered casserole in a 350 degree oven.