In a small bowl, combine the chopped red onion, fresh lime juice, olive oil, kosher salt, and black pepper. Let the mixture sit for at least 5 minutes to soften the onion's flavor.
In a large mixing bowl, add the chopped shrimp, diced avocado, tomato, and jalapeño.
Pour the lime dressing over the shrimp mixture.
Add the chopped cilantro.
Gently toss everything together until evenly coated, taking care not to mash the avocado.
Taste and adjust the seasoning with additional salt and pepper if needed.
Serve your Zesty Lime Shrimp and Avocado Salad immediately, or chill for 10–15 minutes before serving for even better flavor.