01 - In a shallow bowl, whisk together olive oil, lime juice, cumin, smoked paprika, garlic powder, sea salt, and black pepper until thoroughly combined.
02 - Add the fish fillets to the marinade, turning to coat completely. Let marinate for 15 minutes at room temperature.
03 - Preheat grill to medium-high heat (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 the fish is opaque throughout and flakes easily with a fork. Remove from heat and let rest for 5 minutes.
05 - While the fish grills, combine sour cream (or Greek yogurt), lime juice, chopped cilantro, salt, and pepper in a small bowl. Mix until smooth and refrigerate until serving.
06 - Place corn tortillas on the grill for 30 seconds per side until warmed and pliable. Stack on a plate and cover with a clean towel to retain heat.
07 - Using a fork, flake the rested grilled fish into large chunks, discarding any skin.
08 - On each warmed tortilla, layer shredded red cabbage, grilled fish chunks, diced tomatoes, sliced avocado, crumbled cheese, and fresh cilantro. Drizzle generously with the 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.