Pre-heat your broiler to high
Combine the Mayo, Cheese, green onions and lemon juice, to form a paste. Salt & Pepper the whitefish.
Place your fish on a aluminum foil lined baking sheet or pan. (easier for cleanup).
Slather the mayo/Parmesan paste on the whitefish
Broil for 5-6 minutes, depending on thickness of the fish.
Remove from the heat when cooked thru, then cut into serving size pieces. This should be served hot.