Preheat your grill, oven, or a large pan over medium-high heat.
In a small bowl, mix together the chili powder, cumin, paprika, garlic powder, salt, and pepper.
Season the halibut fillets on both sides with the seasoning blend.
Grill, bake, or pan-fry the halibut until it is cooked to your desired level of doneness.
Flake the halibut into small pieces using a fork.
Assemble the tacos by placing a few pieces of halibut in each tortilla, and topping it with the shredded cabbage, diced tomatoes, onions, and cilantro.
Squeeze a lime wedge over the top.
Serve the tacos immediately, and enjoy!
Alternatively, you can also use a store-bought taco seasoning blend in place of the homemade blend. Just follow the instructions on the package to season the halibut before cooking it. Enjoy!