Ceviche is a traditional dish in which seafood is "cooked" by the acid of citrus juices and vinegar. The fish and shellfish need to be very fresh, and the shellfish need to marinate for at least 12 hours, so start this a day in advance. Use a glass dish to avoid reactions with the citrus juice.
1 lb. fresh boneless fish fillets (any mild white fish is best, but salmon is wonderful too)
1. Wash all seafood very well and remove skin and shells. Break fish into small chunks, watching for bones. Cut larger scallops in half, and shrimp into thirds.
2. Combine juices, vinegar, and a small dash of salt. Mix well.
3. In a glass casserole or baking dish, layer shellfish and cover with half the juice mixture. Marinate at least 12 hours, turning to "cook" evenly.
4. In a separate glass dish, layer fish and cover with remaining juice mixture. Marinate for 4-6 hours, turning to "cook" evenly, until fish is firm and looks "cooked" through - it should be opaque white (or very light pink with salmon).
5. Once shellfish and fish are "cooked," drain in a plastic colander.
6. Combine tomato, onion, pepper, cilantro, and oil. Gently mix with fish and shellfish. Garnish with citrus wedges and cilantro, and serve immediately.