take 2 sheets of foil,and put butter on it,then lay on a bakeing pan. Place fillet on foil. Place 1/2 slice bacon ,one slice of tomato,onion,and dot of butter.Add a pinch of salt and pepper. loosly wrap fish in foil.Sealing well.
Do the same with 3 more fillets. Place on grill over med heat, When top of foil puffes up, cook for 3-4 more min. Pierce foil to let out steam. Open and serve.