Pat the fish filets dry. Cube the fish into bite-sized pieces and squeeze all the lime over the fish. All of the fish should be completely covered in lime juice.

Let this sit in the fridge, covered, for 30 minutes.

While the fish is soaking in the lime juice, dice your onion, tomato, avocado, jalapeño (seeds and membranes removed), and cilantro.

Drain the juice from the fish.

Stir the fish with all of the other ingredients until everything is evenly distributed.

Mix and chill and eat.