Place the grouper fillets on a greased baking tray. Brush them with lemon juice. In a small bowl, stir together the Parmesan cheese, butter, mayonnaise, hot pepper sauce, salt and pepper. Set aside.
Broil the fillets for 4 to 6 minutes, until they can be flaked with a fork. Remove from the oven and spread the cheese mixture on top of fillets.
Return to the broiler for an additional 30 seconds, or until the topping is browned and bubbly.