Make the salsa. It's best to make this a little bit in advance for the flavors to develop. If you have time, you can make a day or two ahead of time.
Make the blackening spice blend. Add all of the spices to a small bowl and mix until the ingredients are combined.
Thinly slice the cabbage and dress it with the juice of half a lime, about 1 tablespoon.
Pat the fish dry on a paper towel-lined plate to remove as much moisture as possible.
Generously coat with the blackening seasoning on both sides. To secure the seasoning, pat the fish with your hands.
Heat a skillet over medium heat. Add the oil. Cook the fish in the hot skillet for 2-3 minutes per side, or until a dark crust forms and the fish is cooked through. It should flake easily when it is ready.
Optional, while the fish is cooking: char your tortillas over the burner of a gas stove. This can also be done directly on the grates of a grill.
Assemble the tacos. Place the fish in a warm tortilla, top with pico de gallo, shredded cabbage slaw, and cilantro lime crema to taste.