Start by preheating your oven to 400°F (200°C). This ensures that your tilapia will cook evenly and the topping will get nice and crispy.
In a mixing bowl, combine the softened butter, mayonnaise, fresh lemon juice, dried basil, ground black pepper, onion powder, celery salt, and grated Parmesan cheese. Mix until well combined. The mixture should be creamy and spreadable.
Place the tilapia fillets in a single layer in your prepared baking dish. If the fillets are frozen, make sure they are completely thawed and patted dry with paper towels to ensure the topping adheres well.
Using a spatula, evenly spread the Parmesan mixture over the top of each fillet. Make sure to cover them well for that delicious, cheesy crust.
Place the baking dish in the preheated oven and bake for 15-20 minutes, or until the fish flakes easily with a fork and the topping is golden brown. The exact time may vary depending on the thickness of your fillets.
Once baked, remove the dish from the oven and let it cool for a few minutes. Serve your Parmesan Tilapia with a side of steamed vegetables, rice, or a fresh salad for a complete meal.
