Combine onion, lime juice, olive oil, and 1 tablespoon chopped cilantro in a small bowl, stirring with a whisk. Add shrimp and avocado; toss gently to combine. Divide mixed greens among 4 salad plates; top evenly with shrimp mixture. Sprinkle evenly with 1 tablespoon cilantro.
I made this into 2 servings for a dinner-sized salad and served it with some naan.
