Advance preparation: With stem ends down cut tomatoes into wedges, cutting to, but not through base.
Spread wedges apart slightly; salt lightly.
Combine shrimp, pea pods, and onion.
Mix remaining ingredients and dash pepper; pour over shrimp mixture.
Cover; chill several hours.
Before serving: Drain shrimp mixture, reserving marinade.
Spoon mixture into tomato shells on serving plate.
Pass remaining marinade, if desired.