Carefully chop the fish into bite-size pieces.
In a big bowl, add the chopped onion, cilantro, jalapeno or serrano pepper, green olives and capers. Stir to combine and then add the chopped fish and lime juice. Mix thoroughly again and let sit for one minute. This is when the lime juice will "cook" the fish.
Finish it off by drizzling 2 teaspoons extra virgin olive oil and adding salt and freshly ground black pepper to taste.
Taste the ceviche and add more evoo, lime juice and salt and/or pepper, if desired and to achieve the proper balance of flavors.
Ideally, the fish and vegetables soak up the oil and lime juice so there is little left in the bowl. You do not want a soupy mess.
For best results, serve immediately with a few slices of fresh avocado and crispy tostadas. Add a bowl of homemade salsa and guacamole and a cold adult beverage and you've got a perfect dinner for a hot summer night.