Cut the fish into 1/2 to 3/4-inch cubes. Otherwise, we have everything diced, minced and chopped. We are using a baking dish instead of a bowl so that the fish can sit in a relatively flat layer, to get an even marinade. Add the fish, cilantro, tomatoes, onion, and garlic to a 9”x 13″ baking dish. In a glass, 9x13″ baking dish, place the halibut, tomato, red onion, cilantro, Serrano peppers, and garlic.
Strain fresh-squeezed citrus juice through a fine mesh strainer into a large, glass measuring cup. To the citrus juice, add sea salt and Sriracha; whisk to combine.
Pour the citrus juice mixture over the raw fish mixture. Mix until combined. Cover and place in the refrigerator.
Allow the fish to marinate for 2 hours, uncover, and stir the ceviche. For medium-rare, serve now.
For well-done fish, re-cover and refrigerate for another 2 hours, until the halibut is opaque and cooked through.
Garnish with avocado and scallions, serve with tortilla chips, or over lettuce as a salad.