Soak the beans overnight.

Brown the onion in olive oil in a saucepan. Add 5 glasses of water and let boil. When the liquid comes to a boil, add the cleaned beans, the juice of half a lemon, the sugar and a little salt. Cook until the beans begin to decompose. Put through a vegetable mill. transfer to a serving plate and sprinkle with lemon juice and a fine stream of oil.