On a parchment lined sheet pan, lay out the fish in a single layer. In a small bowl combine the chili powder, cumin, paprika, cayenne pepper and good pinches of salt and pepper. Mix to combine.
Drizzle the fish with olive oil on both sides, and then sprinkle the fish, on both sides, with the spice rub. Use your hands to gently rub the spices into the fish.
When ready to cook, heat a cast iron pan over medium high heat. Cook the fish about 5 minutes per side, until it easily flakes with a fork.
Remove to a platter, sprinkle with lime juice and assemble the tacos!
Layer pieces of fish on warm tortillas. Top with slaw, salsa, crema and guacamole. Garnish with a few sprigs of fresh cilantro.