In a small bowl, mix together paprika, salt, pepper, garlic powder, red pepper flakes, oregano, and thyme.
Rub spice mix all over both sides of the fish.
Heat canola oil in a large skillet or grill pan over high heat. Once the oil is shimmering, place fish in the pan and immediately add butter. Cook fish for about 4 minutes on one side to blacken, flip and cook for another 3 minutes on the other side. Remove to plate to rest for a few minutes.
While fish is cooking, put shredded cabbage, red onion, scallions, cilantro, and lime juice in a medium bowl. Toss to combine.
Warm tortillas on both sides in a skillet over high heat or in a microwave.
Put some of the cabbage mixture on each tortilla. Using a fork, flake fish and put over the cabbage. Top with tomatoes and cheese.