Step 1: Preheat the oven to 400°F (200°C).
Step 2: In a mixing bowl, combine the softened butter, mayonnaise, lemon juice, Parmesan cheese, dried parsley, ground black pepper, garlic salt, onion powder, and celery salt. Mix well until creamy.
Step 3: Place tilapia fillets on a greased baking sheet, spread out evenly.
Step 4: Generously spread the topping mixture over each tilapia fillet.
Step 5: Bake in the preheated oven for 15-20 minutes until the tilapia is cooked through and the topping is golden brown.
Step 6: Let cool for a few minutes, then serve hot, garnished with parsley or lemon wedges.
