Rinse and dry the fish and score it four times diagonally to the body with a kitchen knife. Place on a platter, baste with lime juice and set aside.
Remove skin from sweet potatoes and cut into narrow slices. Place in water and gently toss until just al dente. Drain and set aside as well.
Meanwhile, pluck the oregano leaves from the stems. Grind the garlic with the salt and oregano in a mortar. Divide the paste evenly among the four incisions in the fish. Halve and seed the bell bell pepper, remove the white pulp, and cut the bell pepper into rings. Cut the onion into narrow rings.
Preheat the oven to 180 °C. Brush an ovenproof dish with enough oil and cover the bottom with potato slices. Place the fish on top and spread half of the bell pepper and onion rings evenly over it. Grind one bay spice and sprinkle over the fish, evenly distribute the others around the fish. Drizzle oil over the top and generously sprinkle with black pepper. Stir the vinegar with tomato puree, wine and sugar and pour over the fish. Top with the remaining onion and bell pepper rings, drizzle with the remaining oil. Bake the fish loosely covered with foil for thirty minutes.
Remove the foil and cook for another ten to fifteen minutes.
Serve with chopped parsley and lime slices.
Serving: Long grain rice