If preparing indoors, preheat the oven to 200°C/400°F/Gas 6. Tear off 4 sheets of aluminum foil into sections large enough to fold over fillets, with another couple of inches on each side to seal.

Place one fillet slightly off-center on each sheet and add 3 lemon slices and 2 lime slices on top of each. Sprinkle one-quarter of the cilantro and jalapeno pepper over each fillet, and top with one tablespoon of butter. Season with salt and black pepper, to taste.

Fold the aluminum foil in half over the ingredients. Fold the 3 open sides, one at a time, over several times to seal the packet completely. Seal the packet tight enough to hold in the steam, but allow enough room for the air to expand.

.Place the foil packets in the center of the preheated oven for 15 minutes, or place on hot grill over medium, direct heat and cook for approximately 8-10 minutes.

Remove from oven (or grill) and carefully open the foil packets to avoid the hot steam. Discard the lemon and lime slices. Transfer fillets to individual serving plates, if desired, or leave inside foil packets and serve with your choice of sides Enjoy!