Heat a large oven-proof skillet with 2 tsp oil over medium heat.
Add onions and cook for 20 minutes, or until caramelized, stirring occasionally.
Add Worcestershire sauce and vinegar and stir to mix.
Remove onion mixture from pan and set aside.
Preheat oven broiler on high.
Wipe skillet and return it to stove over medium high heat.
Add 3 tsp oil.
Combine flour and spices in a shallow bowl.
Coat Catfish in mixture and shake off excess.
Cook seasoned fillets for 5 minutes, then flip and continue cooking for 5 minutes.
Top fillets with onion mixture and sprinkle with cheese.
Place under broiler for 3 minutes or until cheese is beginning to brown.