To prepare the sauce mix the chopped onions, oil, lemon juice and seasoning, set aside to flavor for 10 minutes .

Slice fine the fish. Seed the sweet peppers, dice and simmer in some salted water for 2 minutes.

Scald, peel and seed the tomatoes, dice the pulp.

Combine the ingredients, dress with the sauce and refrigerate for 30 minutes.

When serving garnish with egg slices and lettuce leaves.