Preheat grill plate or grill pan over medium heat.
Quarter limes.
Chop prawns into bite-sized pieces.
Cook prawns on the grill plate, stirring, until the meat turns white and edges lightly charred, about 3-4 minutes.
Meanwhile, char limes by cooking, cut-side down on the hot grill plate.
Cut avocado into small chunks.
In a small bowl mix together the apple cider vinegar, olive oil, salt and pepper. Add juice from one whole charred lime. Add grilled prawns and mix well.
Heat tortillas on the grill or in a grill pan.
To serve, place 1-2 tablespoons of the prawns and avocado salsa on top of the tortilla, top with coriander leaves and red salsa sauce.