1. Preheat the oven to 400°. In a heavy 8- to 10-inch skillet, heat the olive oil until a light haze forms above it. Add the onions and cook over moderate heat, stirring frequently, for 5 minutes, or until the onions are soft and transparent but not brown.
2. Stir in the olives, fresh red pepper or pimiento, fresh coriander and ground annatto seeds, and cook, stirring occasionally, for 3 minutes longer. Then add the orange juice, lemon juice, salt and a few grindings of black pepper.
3. With a tablespoon of soft butter, grease the bottom and sides of a shallow heatproof casserole large enough to hold the fish comfortably. Place the fish in the casserole and pour the sauce over it.
4. Bake, uncovered, in the middle of the oven for 30 minutes, basting the fish with its sauce every 10 minutes. The fish is done if its flesh feels firm when pressed with a finger. Be careful not to overcook.
5. Serve the baked fish directly from the casserole, sprinkled with the chopped egg, or-with one or two spatulas-transfer the fish carefully to a large heated platter, pour the sauce over and around it and garnish with the chopped egg or with the shredded lettuce and radishes.
