1. Place butter in 1 1/2-quart (10x6) glass baking dish.
2. Microwave on ROAST for about 1 1/2 minutes or until melted. Add mustard, parsley flakes, garlic powder and lemon juice. Cut each fillet into 4 pieces. Dip in seasoned butter; arrange with thick edges toward outside of dish. Cover with plastic wrap.
3. Microwave on HIGH for 6 to 7 minutes or until fish flakes easily. Let stand, covered, 5 minutes before serving.