Rub fillets with lemon wedge and rinse under cold water.Place in baking pan and squeeze lemon over fillets and sprinkle on salt ,pepper,garlic powder. Thinly slice onion and cover fillets. Now pour tomato sauce covering fillets and onion. Sprinkle on oregano,parsley and then a good coating of parmesan cheese over everything. preheat oven to 425 degrees and bake for 18 minutes but check it for flaking so you don't over cook it.
Other Notes:
My friends and family love this recipe. Only use fillets from smaller blues,nothing over 8lbs. Bleed,gut and ice them right away. Use only white meat fillets and cut out any dark meat muscle. Plan on eating them that night or the next day.DO NOT FREEZE!! Eat them fresh please.