1. Prepare the Fish:

• Begin by ensuring that your fish is extremely fresh. Ceviche is traditionally made with raw fish, so freshness is key.
• Cut the fish fillets into small, bite-sized cubes (about 1/2-inch pieces). Place the fish into a large, shallow glass or ceramic bowl.

2. Marinate the Fish:

• Squeeze fresh lime juice over the fish until it is completely covered. The lime juice “cooks” the fish by denaturing the proteins, turning it opaque and firming it up.
• Add the orange juice (if using), which adds a touch of sweetness to balance the acidity of the lime.
• Stir the mixture gently to ensure that all the fish pieces are coated with the juice.
• Cover the bowl with plastic wrap and refrigerate the fish for 30 minutes to 1 hour, depending on how much you want the fish to “cook” in the lime juice. If you prefer your fish slightly raw, 30 minutes is enough. If you like it more “cooked,” marinate for an hour or more.

3. Prepare the Vegetables:

• While the fish is marinating, prepare the red onion, tomatoes, cilantro, and jalapeño (if using).
• Chop the onion and tomatoes into small, uniform pieces.
• Finely chop the cilantro.
• If you’re using jalapeño, be sure to remove the seeds if you prefer less heat. You can substitute with a bell pepper for a milder version.

4. Assemble the Ceviche:

• Once the fish has marinated to your liking, gently stir the fish mixture to ensure the lime juice has fully infused the fish.
• Add the chopped vegetables (onion, tomato, cilantro, and jalapeño or bell pepper) to the fish and lime mixture. Mix gently to combine.
• Season the ceviche with salt, black pepper, and ground cumin (if using) to taste. Stir everything together gently.
• If you prefer a richer taste, you can add a tablespoon or two of olive oil to the ceviche for extra depth of flavor.

5. Chill and Serve:

• Once all the ingredients are combined, cover the ceviche again and refrigerate it for another 15-20 minutes to let the flavors meld together and chill.
• Taste the ceviche before serving and adjust the seasoning if needed, adding more lime juice, salt, or pepper as necessary.

6. Serve:

• Serve the ceviche in small bowls or glasses. It is traditionally accompanied by tortilla chips, plantain chips, or saltine crackers.
• Garnish with extra cilantro or a lime wedge for extra freshness.