Pat fish fillets dry with paper towels to help seasoning stick and get a crispy crust.

Mix blackening seasoning if making from scratch. Thinly slice red cabbage and chop cilantro. Halve lime and mince garlic. Scoop avocado flesh into a bowl.

In the bowl with avocado, add Greek yogurt, lime juice, minced garlic, chopped cilantro, a pinch of salt, and black pepper. Mash and mix until smooth and creamy. Adjust lime or salt to taste.

Sprinkle blackening seasoning evenly over both sides of the fish and press lightly to help it stick.

Heat olive oil in a skillet over medium-high heat until shimmering. Add fish fillets and cook undisturbed for 3-4 minutes until edges look opaque and crust forms. Flip and cook another 3 minutes or until fish flakes easily. Thicker fillets may need 1-2 minutes more.

Warm tortillas in a dry skillet over medium heat for 20-30 seconds per side or wrap in foil and heat in a warm oven.

Break cooked fish into chunks and spoon onto each tortilla. Drizzle generously with creamy avocado sauce. Top with shredded cabbage, extra lime squeeze, cilantro, or black pepper as desired.

Serve immediately while warm.