Heat the oven to 425°F (220°C) and line a baking sheet with parchment. Pat the fish dry and place it on the sheet.
Mix the chili powder, paprika, cumin, garlic powder and 3/4 teaspoon of the salt. Brush the fish with the oil and sprinkle the spice mix over both sides.
Bake for 8–12 minutes, depending on thickness, until the fish is opaque and flakes easily with a fork.
Meanwhile, toss the cabbage and cilantro with the juice of one lime and the remaining salt. Set aside to soften slightly.
Stir together the yogurt, mayonnaise, hot sauce and a squeeze of lime juice to make the sauce.
Warm the tortillas in a dry skillet or wrapped in foil in the oven. Flake the fish into large pieces and fill each tortilla with fish, slaw, avocado and a spoonful of sauce. Serve with lime wedges.