Prepare the Fish:
Preheat the oven to 375°F (190°C). Line a baking sheet with parchment paper or a silicone mat.
Pat the tilapia fillets dry with paper towels. In a small bowl, combine cumin, cayenne pepper, paprika, salt, and black pepper.
Sprinkle the seasoning mixture evenly on both sides of the tilapia fillets.
Drizzle the fish with olive oil and dot each fillet with unsalted butter.
Bake the fish for 20-25 minutes or until it is opaque and flakes easily with a fork. For extra crispy edges, broil for an additional 3-5 minutes.
Prepare the Taco Sauce:
In a medium bowl, whisk together sour cream, mayonnaise, lime juice, garlic powder, and sriracha sauce until smooth and well-combined.
Taste and adjust the sriracha based on your desired spice level.
Toast the Tortillas:
Heat a large, dry skillet or griddle over medium-high heat.
Toast the tortillas for about 30 seconds per side, just until warm and slightly crispy.
Assemble the Tacos:
Start by placing a piece of tilapia on each tortilla.
Add shredded cabbage, avocado slices, diced tomatoes (if using), red onion, and cilantro.
Drizzle with the taco sauce and finish with a sprinkle of Cotija cheese.
Squeeze fresh lime juice over the tacos before serving.