Directions. 1  Preheat oven to 350. 2  Lightly grease/spray a large shallow baking dish. 3  Pat haddock dry; arrange in prepared baking dish. 4  Sprinkle w/ salt and pepper. 5  In a small bowl, mix together melted butter, lemon juice and minced garlic; evenly brush over haddock fillets. Sprinkle w/ salt and pepper. 2  In a small bowl, mix together melted butter, lemon juice and minced garlic; evenly brush over haddock fillets. 3  Evenly sprinkle fillets with parsley tarragon and paprika. 4  Bake at 350 for 25-35 minutes of until opaque and flakes easily.