Place fish onto large pieces of foil. Make three deep incissions with sharp knife on each side of fish.
In a food processor, combine onion, garlic, ginger, lemon rind, tamarind sauce, light soy sauce and peanut oil, blend until the mixture is smooth.
Spread mixture on both sides and inside the fish.
Wrap foil around fish, secure firmly. Place fish in a baking dish, bake at 350° F for 30 minutes, or until fish is just cooked.Servings: 4