peeled and deveined raw medium shrimp • freshly squeezed lemon juice (from 2 lemons) • freshly squeezed lime juice (from 2 to 3 limes) • medium tomatoes, seeded and chopped • small red onion, finely chopped • medium jalapeño, seeded and finely chopped (about 3 tablespoons) • chopped fresh cilantro leaves and tender stems • kosher salt • medium avocado (optional)