01 - In a shallow bowl, whisk together olive oil, lime juice, ground cumin, smoked paprika, garlic powder, sea salt, and black pepper until well combined.
02 - Add white fish fillets to the marinade, turning to coat evenly. Let stand for 15 minutes at room temperature.
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 just cooked through and easily flaked with a fork. Transfer to a plate and let rest for 5 minutes.
05 - While 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 slightly charred. Keep wrapped in a clean kitchen towel to maintain warmth.
07 - Flake the grilled fish into large chunks using a fork, discarding any skin or bones.
08 - Layer each tortilla with shredded red cabbage, grilled fish chunks, diced tomatoes, sliced avocado, crumbled cheese, and fresh cilantro. Drizzle with the prepared sauce.
09 - Arrange tacos on a serving platter with lime wedges on the side. Serve while warm.