Place oven rack in its highest position and turn the oven on to broil. Line a heavy baking sheet with foil and lightly coat with cooking spray.
In a small bowl combine the Parmesan cheese, butter, mayo, lemon juice and basil.
Season tilapia with salt and pepper and place on the prepared baking sheet.
Broil tilapia for 2 to 3 minutes. Flip each fillet over and broil another 2 to 3 minutes. Spread fillets with Parmesan mixture and place under the broiler for another 2 minutes or until lightly browned. Serve topped with fresh chopped parsley if desired.
Notes
To soften butter on short notice, microwave on 30% power 15 to 30 seconds.