Soak codfish in water to cover for 4 hours. Drain well. Boil codfish in enough water to cover for 15 minutes. Drain and rinse in fresh water. Discard skin and bones, and shred flesh.
Arrange codfish on a platter. Garnish with onions and tomato slices.
Combine ingredients included in C to make a sauce. Pour sauce over fish, chill, and ser