Preheat oven to 180 degrees C. Rinse fish fillets under cold water and pat dry with paper towels.
Prepare a 15x23cm oven-proof casserole dish by rubbing bottom with 1 tablespoon of butter. Place fish fillets in a single layer in the prepared dish.
Brush the tops of the fillets with lemon juice, turn over and brush the other side with lemon juice.
Bake in preheated oven for 10 minutes or until the fish just begins to flake; Do not overcook.When fish is baked, remove from the oven.
Meanwhile, in a bowl, combine cheese, remaining 1 tablespoon of butter, mayonnaise, spring onion, garlic, cayenne, paprika, basil, black pepper, and Tabasco sauce.
Turn the broiler onto HIGH to preheat.
Spread the cheese mixture over the fish fillets and place under the broiler, just below it and broil on HIGH for 2 minutes or until a light golden brown. This time seems to work real well and you do not want to overcook the tilapia.