Place fillets (pat dry) on parchment paper. Rub salt and pepper on the fillets.
Rub some butter on the aluminum foil, and place some onions on the foil. Then place fish on top of the onions.
Cover with remaining onion, herbs and bay leaves.
Drizzle olive oil, lemon juice over the fish and add remaining butter. Fold and seal fish with aluminum foil.
Place on tray and bake in a preheated 375F (190C) oven for approximately 8-10minutes (~8 minutes per pound).
Remove from the oven and allow to stand for 3-4 minutes without opening the bag.