Peel and finely chop the onion. Wash and clean the zucchini and tomatoes. Cut tomatoes into quarters and remove seeds. Halve, clean and wash the bell peppers. Cut vegetables into strips. Wash thyme, shake dry and pluck the leaves from 4 stems and chop them coarsely
Heat 2 tablespoons of oil in a frying pan. Sauté the onion and bell pepper for about 4 minutes, then add the courgette. Steam for another 3 minutes. Add tomatoes and thyme, heat briefly, season with salt and pepper
Wash the fish, dab dry and season with some salt and lemon juice. Place a piece of foil on the work surface. Place slices of ham on top, slightly overlapping. Place fish fillet on top and cover with vegetables. Place a second fish fillet on top. Wrap the fish in ham and tie with kitchen string
Place the fish on a greased baking tray and sprinkle with 3 tablespoons of olive oil. Cook the fish in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 20 minutes while turning. Remove, sprinkle with remaining thyme and coarse pepper and serve