Preheat oven to 425 degrees F (220 degrees C). Place steelhead in shallow baking dish. Melt butter in a small skillet set over medium heat. Add garlic and cook until it softens, about 3-4 minutes. Mix in lemon juice and dill and then spoon over fish. Season with salt and pepper. Bake 12-15 minutes, or until fish begins to slightly flake. Divide fish and pan juices among 4 plates.