Preheat broiler. Cut lemon in half; juice one half and slice the other half into 4 slices to serve with fish.
Combine dill weed, onion salt, garlic powder, lemon juice, and melted butter. Place salmon steaks on broiler pan. Baste top side up with one half of the butter mixture. Broil about 4 minutes. Turn fish and baste with other half butter mixture. Broil until slightly firm to touch and opaque in center.