In a large saucepan, fry the chopped onion in  an abundant quantity of olive oil. Add chopped squid, cook it on a low heat, and cover them with the same fish soup, two ladles of tomato paste and zafferanella, salt and pepper. Place the fishes on different layers, by arranging the most tender fishes at the end; cook for other 15/18 minutes. Once cooked, put the slices of toasted bread on the dishes and cover them with the fish and sauce. Serve it as one-plate meal accompanied by dry white wine or young red wine or a fresh rosé wine.