Preheat oven to 400 degrees. Pour 4 Tbsp of the melted butter into a 2-qt casserole dish and set aside.

Season both sides of fish with salt and pepper and place into casserole dish on top of melted butter. In a small bowl, stir together breadcrumbs, lemon zest and parsley then drizzle in remaining 2 Tbsp of melted butter. Toss with a fork until breadcrumbs are evenly coated in butter then divide crumb mixture evenly over the top of the cod filets.

Bake 18-20 minutes or until cod is cooked through and flakes easily when pierced with a fork.

Remove from oven and transfer fish to serving platter. Add a few drops of lemon juice to the butter remaining in the baking dish and season to taste with salt and pepper. Drizzle butter sauce over fish filets and serve immediately.