2 lg. bluefish fillets
1 lg. yellow onion
1 stick butter
Juice of 1 lemon
12 oz. mayonnaise
6 oz. jar Dijon mustard

Start by preheating oven to 350 degrees. While the oven heats, wash fillets thoroughly. Don't pat them dry, just put them into a large baking dish. Next, slice 1 large onion into very thin slices. Place the onion rings all over the fillets.