Slice the fish into 5cm/2inch fingers (this size is perfect for tacos).
Drizzle the olive oil and lime juice over the fish then generously season with the taco spice and salt on both sides.
Heat a large pan or skillet over medium-high heat then add the fish and allow to cook for 1-2 minutes per side (depending on thickness) until cooked through and caramelized.
Remove from the pan and allow to rest for a few minutes.
Halve the avocados and scoop out the flesh. Mash with the back of a fork then season with lime juice, salt and pepper.
Char the tortillas over an open flame (your gas stove) or in a hot pan.
Add a smear of avocado to every tortilla then top with a piece of fish, a generous dollop of salsa, pickled onions, sliced chillies and coriander/cilantro. Serve immediately.