• 1 pound fresh, skinless snapper, bass, halibut or other ocean fish fillets, cut into 1/2 inch dice
• 1 1/2 cups fresh lime juice
• 1 medium white onion, chopped into 1/2 inch pieces
• 2 medium large tomatoes, about 1 pound, chopped into 1/2 inch pieces
• Fresh hot green chiles: 2 to 3 serranos or 1 to 2 jalapeños, stemmed, seeded and finely chopped
• 1/3 cup chopped cilantro, plus a few leaves for garnish
• 1/3 cup chopped pitted green olives, manzanillas for a typical Mexican flavor
• 1 to 2 tablespoons extra virgin olive oil, optional
• Salt
• 3 tablespoons fresh orange juice or 1/2 teaspoon sugar
• 1 large or 2 small ripe avocados, peeled, pitted and diced
• Tostadas, tortilla chips or saltine crackers, for serving

In a 1 1/2 quart glass or stainless steel bowl, combine the fish, lime juice and onion. Use enough juice to cover the fish and allow it to float freely; too little juice means unevenly "cooked" fish. Cover and refrigerate for about 4 hours, until a cube of fish no longer looks raw when broken open. Drain in a colander. In a large bowl, mix together the tomatoes, green chiles, cilantro, olives and optional olive oil. Stir in the fish and season with salt, usually about 1/2 teaspoon. Add the orange juice or sugar. Cover and refrigerate if not serving immediately. Just before serving, gently stir in the diced avocado.