In a small bowl, whisk together all the spices for the blackening seasoning. You may have some leftovers which can be stored in an airtight container for up to 3 months.

Place the fish in a baking dish or other container and season liberally with blackening seasoning. Reserve 1 teaspoon of seasoning for the white sauce. Let the fish sit in the seasoning blend for at least 30 minutes, up to 3 hours.

Whisk together the mayonnaise, sour cream, lime juice, and 1 teaspoon of blackening seasoning until smooth. Refrigerate until ready to use.

Melt the butter in a large nonstick skillet over medium heat. Once the butter is melted and foamy, add the fish in a single layer. Depending on how many pieces, you may want to cook them in batches. Cook for 3-4 minutes per side, until browned and the fish is cooked through and flaky.

Gently flake the fish into large chunks and assemble on warmed corn tortillas topped with cabbage, pico de gallo, and some of the sauce. Serve with lime wedges on the side.