For marination, grate the onion with the fine part of the grater, squeeze the juice and place it in a bowl. Add olive oil and freshly squeezed orange juice, finely chopped rosemary leaves and freshly ground black pepper and mix.
Place the bonitoes in the sauce and let them sit for half an hour. Rub the fish all over with your hands from time to time to absorb the sauce thoroughly. Place the fish on a baking tray lined with baking paper and bake it in a preheated oven at 180 degrees for 40 minutes.
