En papillote is a classic method of cooking food wrapped in parchment paper. It’s an easy and healthy way to steam food and infuse flavor. The traditional method of using parchment paper requires origami-style folding and results in a beautiful, elegant presentation; aluminum foil works too. The paper rises while cooking, and is filled with the fragrances of the fresh ingredients. When you open the parchment you get the gift of this wonderful aroma. The rule of thumb for cooking fish is 10 minutes of cooking time, per inch of thickness. The fish will flake easily when cooked through.
Pre-heat the oven to 400 degrees. Line a large baking sheet or roasting tray with a long piece of parchment, enough to fold half over the fish fillets. Sprinkle one half of the parchment with olive oil and lay the slices of lemon over the oil. Place the fish fillets, skin side down on top of the lemon slices. Sprinkle with salt and pepper. Top the fish with the cherry tomato halves and sprigs of thyme. Spoon the water or white wine over the fish fillets and a splash of olive oil, if preferred. Fold the other half of parchment over the fish and crimp the edges, pressing down tightly. Start in one corner and go all the way around to the other corner.
Bake the fish for 12-18 minutes, depending on the thickness of the fish. The parchment will be browned and puffed up. You can snip the parchment open with scissors or unwrap it. Serve the fish with the lemon slices and the sauce from the pan.