Arrange prawns on a baking sheet and roast for 6 to 8 minutes. Broil for the last minute for a light char. Optional, roast the jalapeno at the same time to use for the salsa.
Salsa:
Chop pineapple, tomatoes, onion, cilantro, and jalapeno and add to a bowl.
Mix in lime juice, salt, and pepper.
Tacos:
Warm the tortillas and add smashed avocado, prawns, and the pineapple salsa.