Place chickens in a pot with all the other ingredients except olives and lemon peel. Cover with water and bring to a boil, turning the chickens over to make sure they are well coated with the sauce. Cook over moderate heat, covered, adding a little wateer if necessary, and basting the chickens with sauce from time to time. Remove the onion as soon as it is cooked.
When chickens are done, add the olives and the lemon peel, a let simmer a few minutes longer. To serve place the chickens on a serving platter, top with olives and lemon rinds, and pour sauce over the whole dish.