Preheat the oven to 350 degrees F.
Line an oven tray (cookie sheet) with parchment paper. Take a large piece of foil (large enough to fully wrap the fish like a present) and put it on the oven tray. Butter the foil. Combine the 4 tablespoons of butter and the shallots in a small bowl and set aside. Put the fish in the center of the foil. Season the entire fish with the shallot butter, inside and out and sprinkle with the salt and pepper. Put the thyme sprigs inside cavity and top the fish with lemon slices. Fold the edges of the foil over fish and seal.
Bake the fish until cooked through, about 45 minutes. Transfer the fish to a platter. Open the foil and serve.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.