1-Getting Started with Prep Work: First, gather and prepare all your items to make things flow easily. Thinly slice the 1/2 red onion and chop the other fresh ingredients like cilantro and jalapeño. Dice the 1 pound of fresh ocean fish into small, 1/2 inch cubes to ensure even marinating. This step takes about 15 minutes and helps everything mix well later.

2-Mixing and Marinating the Base: Next, in a glass or ceramic bowl, combine the fish with 3/4 cup fresh lime juice so it’s fully covered. Add the sliced red onion, 1 to 1 1/2 teaspoons kosher salt, 1/4 teaspoon black pepper, 1 to 2 minced garlic cloves, and the chopped serrano or jalapeño. Mix it gently and pop it in the fridge for 15-20 minutes. This lets the lime juice work its magic, giving you that fresh, ‘cooked’ texture without heat.

3-Adding the Extras and Finishing Up: Once the fish has marinated a bit, stir in 1 cup of halved or diced grape or cherry tomatoes, 1 cup diced cucumber, 1/4 to 1/2 cup chopped cilantro, and 1 tablespoon olive oil if you like. Give it another gentle toss and let it chill for another 10 minutes. Before serving, taste and tweak the salt or heat as needed, then fold in the diced avocado. The whole process, including a 45 to 60 minutes marinating time, wraps up in about 55 minutes total.