1. Cut 2 or 4 large squares of tinfoil and lightly grease with a little oil.
2. Place a fillet in the centre of each square and add the thyme, lemon zest, a knob of butter, a pinch of salt and a good twist of ground black pepper.
3. Bunch the foil to form a parcel with a good pocket of air inside and place them on a baking sheet.
4. Cook in a preheated oven 180°c for 12 minutes.
5. It is possible to serve these parcels still in the foil, or alternatively empty the fish onto a warm plate, pouring any juices over the top of the fish.
6. This fish will go well with some new seasons asparagus and buttered new potatoes.