Combine the avocado, lime juice and cilantro, if using, in a bowl, and set aside.
Place the oil in a skillet over medium-high heat. Add the onion and bell pepper and cook until tender, about 3 to 4 minutes. Mix in the prawns, orange juice, cumin, Tabasco and salt. Cook until the prawns are heated through, about 2 to 3 minutes.
Divide and stuff the tacos with the lettuce, prawn mixture and cubed avocado.
Recipe Options: For a spicy, fresh pepper taste, finely chop a small- to medium-sized jalapeno pepper and add it to the skillet when cooking the green bell pepper. Instead of chopped prawns, use 300 grams of the smaller, cooked salad shrimp in this recipe.