Preheat the oven to 375 degrees Fahrenheit. Prepare a shallow baking sheet by lining it with parchment paper.
Run the tilapia fillets under cool water. Gently dry them by patting the fillets with clean paper towels. Make sure that the fillets are completely dry. Rinsing the fillets is an optional step, but it comes in handy if the fillets are partially frozen and in need of thawing or if they are fresh and covered in a sticky coating.
Mix the lemon juice and melted butter.
Transfer the fillets to the prepared baking sheet. Place the tilapia on the sheet in a single layer, spaced apart evenly.
Season the tilapia. Pour the butter and lemon juice mixture over the fillets, spreading it evenly. Sprinkle the tilapia with the black pepper.
If desired, you can add other seasonings to the tilapia at this time, as well. Flavors that complement the taste of lemon include onion, garlic, parsley, dill, basil, and oregano. For concentrated powders like garlic powder or onion powder, use no more than 1/4 tsp (1.25 ml). For herbs, use 1 tsp (5 ml) dried or 1 Tbsp (15 ml) fresh.
Bake the fish. At this temperature, tilapia should be done in about 30 minutes. When done, the tilapia will be completely white all the way through and should flake apart evenly with a fork. If desired, you can add the Parmesan cheese to the fish during the last 5 to 10 minutes.