For ovens with top and bottom elements, please your rack in the middle. For ovens with only a top element, place your rack closer to the bottom. Preheat oven to 365 Fahrenheit.
In a small bowl, mix the dry spices well (cumin, salt, pepper & cayenne)
Line a baking sheet with foil and drizzle it very lightly with a bit of olive oil. Lay the fillets on it and drizzle the rest of the olive oil on them, and spread evenly on the fillets with the back of a spoon. Dab each fillet with a bit of butter, then sprinkle them evenly with the dry spice mix.
Cook for about 20 minutes or until the edges of the fillets start to brown. This will add to your texture.
Remove the fish from the oven and flake the fillets.
Heat your tortillas on a hot skillet or pan as instructed, add your fish and assemble your taco as desired. Guacamole recipe link is below.