Pretty much any white fish is delicious this way:

Thinly slice a lemon and an onion and lay on a piece of foil large enough to wrap your fish. Top with the fish, season with salt and pepper, and any fresh herb you like. Drizzle with olive oil and a splash of vermouth. Seal the foil, place on a baking sheet and bake at 350 for around 20 minutes, depending on the thickness of the fish. For a fancier presentation, use parchment instead of foil. If you slice the lemons thinly enough, you can actually eat the lemon slices, peel and all, along with the fish and onions.