Slice the red cabbage and green cabbage thin.
In a bowl, combine the sliced cabbages with fresh lime juice, olive oil, cilantro, salt, and pepper. Mix well and set aside.
In a separate small bowl, combine chili powder, paprika, ground cumin, garlic powder, onion powder, pepper, salt, and cayenne pepper. Mix well.
Pat dry the thick-cut cod with paper towels and sprinkle the spice mixture on both sides of the fish.
In a skillet, heat olive oil and butter over medium-high heat.
Cook the seasoned fish in the skillet for about 4-5 minutes per side, or until cooked through and blackened.
Remove the fish from the skillet and let it rest for a few minutes.
Warm the flour tortillas in a clean skillet or microwave.
Assemble the tacos by placing the blackened fish on a tortilla, topping it with the cilantro slaw, and drizzling with cilantro lime sauce and salsa.
Serve and enjoy!