With kitchen towels dab the filet to make sure it is dry. Sprinkle the filet on both sides with the salt, pepper and cayenne. Place the filet skin side down in the pan. Sprinkle the zest on the flesh.
Cook until the skin is golden and crisp, about three minutes. Then flip over and continue to cook for another three to five minutes, depending on the level on doneness you prefer.
While the fish is cooking, blend all the ingredients for the puree together. Taste and see whether you would like more basil. Add the lime juice last. Serve the trout with the puree and some more lime wedges on the side. Enjoy!