Line large baking sheet with parchment or silicone liner. In a small dish, combine seasonings: 1/2 tsp cumin, 1/2 tsp cayenne pepper, 1 tsp salt and 1/4 tsp black pepper and evenly sprinkle seasoning mix over both sides of tilapia.
Lightly drizzle fish with olive oil and dot each piece with butter. Bake at 180c for 20-25 min. To brown edges, grill for 3-5 minutes at the end if desired.
Combine all Taco sauce ingredients in a medium bowl and whisk until well blended.
To serve the tacos, toast the corn tortillas quickly on a large dry fry pan or griddle over medium/high heat.
To assemble: start with pieces of fish then add remaining ingredients finishing with a generous sprinkle of cheese and finally that awesome taco sauce! Serve with a fresh lime wedge to squeeze over tacos