Mix the blackened seasoning spices together in a small bowl. Season the fish on both sides with the mixture.
Heat a large nonstick skillet over medium high heat. Add the oil and swirl the pan to distribute the oil evenly. Add the fillets and cook on both sides for 4-5 minutes or until the bottom is browned nicely.
Flip the fillets and cook on the other side until cooked through about 1-2 minutes. The length of cooking time will vary depending on the thickness of the fish.
In the meantime, slice the cabbage very thin and prepare the lime crema. Combine the juice of ½ a lime and mayo in a small bowl. Chop the cilantro and set it aside.
Take the tortillas and place some fish inside along with sliced cabbage, chopped cilantro and the lime crema. Feel free to serve the fish tacos with plenty of sliced avocado and lime wedges!