Haddock Bubbly Bake

2 pounds haddock fillets
salt and pepper to taste
1 10.75 ounce can condensed cream of mushroom soup
1 onion, thinly sliced
1 cup shredded mild Cheddar cheese

Preheat oven to 350F. Lightly butter one deep 9 x 9 inch casserole dish. Layer fish fillets into the bottom of the prepared pan and sprinkle with salt and pepper to taste. Layer onion slices over fish. Spread cream of mushroom soup over all and sprinkle with the shredded cheese. Bake for about 40 minutes or until bubbly and fish is flaky. 

Serves 4 to 6.