Put the oven to heat at 180°c
Mix the cumin, cayenne pepper, salt and pepper
Sprinkle the spice mixture on both sides of the fish and place the filets in a baking paper covered ovenproof dish. The mixture is quite spicy so you can sprinkle less on the filets for those who are reluctant to spicy food.
Top the fish with the olive oil and butter in small pieces and bake until cooked through. Depending on the fish the cooking time can vary from 10-20 minutes.