Pre-heat oven to 350 °F (175 °C) or low broil. (If using low broil place fish on lowest oven rack).
Lay frozen fillet on foil lined baking pan.
Zest lemon and chop onion.
Cover fillet with lemon zest and chopped onion, sprinkle garlic and creole seasoning lightly over fillet. If using butter (optional), melt butter and mix all ingredients together and pour over fish fillet.
Place in pre-heated oven and cook approximately 15 minutes or until fish flakes easily.
There are 243 calories in 1 serving of Spicy Lemon Tilapia.