Cut the sardines behind the head, open on the back side, unfold the fillets, removing the center ridge and bones with your fingers.
Drive behind the center ridge and carefully pull out center ridge along with bones. Then cut fillets small left and right of dorsal line, cut tail small.
Place fillets in a shallow dish. Season the fillets with salt and marinate for about one hour.
Mix the ingredients of the marinade, pour over the fillets and put in the refrigerator form for 120 minutes (better: overnight) covered with cling film.
In a frying pan with olive oil, start by sautéing the peppers and melanzani well, together with freshly chopped rosemary and garlic, then add the mushrooms and finally the zucchini, sautéing everything together well.
At the end, stir in the tomatoes and season with salt and pepper. Put the vegetables in a large enough bowl, stir in the coarsely chopped basil leaves, season well with the juice of one lemon, oil, salt and freshly ground pepper, cool a little.
Remove the sardine fillets from the marinade, arrange on plates and season with salt and pepper. Serve with the lukewarm lettuce.