01 - Whisk together olive oil, lime juice, cumin, paprika, garlic powder, salt, and pepper in a shallow bowl until fully combined.
02 - Add fish fillets to the marinade, turning to coat evenly. Let sit at room temperature for 15 minutes to absorb flavors.
03 - Heat grill to medium-high temperature (approximately 400°F). Lightly oil the grates to prevent sticking.
04 - Place marinated fish on the grill. Cook for 3 to 4 minutes per side until fish is opaque, flakes easily with a fork, and reaches an internal temperature of 145°F. Transfer to a plate and rest for 5 minutes.
05 - Combine sour cream, lime juice, chopped cilantro, salt, and pepper in a small bowl. Mix until smooth and creamy. Refrigerate until assembly.
06 - Place corn tortillas directly on the grill for 30 seconds per side until pliable and lightly charred. Keep warm wrapped in a clean kitchen towel.
07 - Using two forks, break the rested fish into large chunks, about 1 to 2 inches in size, removing any bones if present.
08 - Layer each warmed tortilla with shredded cabbage, flaked fish, diced tomatoes, sliced avocado, crumbled cheese, and fresh cilantro. Drizzle generously with prepared sauce.
09 - Arrange tacos on a serving platter and accompany with fresh lime wedges. Serve immediately while tortillas are warm and fish is hot.