Shrimp Ceviche Cocktail

Ingredients (12)

• 1/4 cup chopped red onion
• 2 small limes
• 1 tsp olive oil
• 1 lb large cooked, peeled shrimp
• 1 medium hass avocado
• 1 medium tomato
• 1 cup diced English cucumber
• 1 serrano pepper
• 2 tbsp chopped cilantro
• salt and fresh black pepper to taste
• 1 lime cut into wedges for serving
• 2 1/4 cups shredded iceberg lettuce