I tried this last night..Walleye fillets (as many as you want)Red onionsTomatoes.Slice up your onion(thin rings)and Tomotoes(thin slices)Place your Walleye Fillets on a buttered cookie sheetSeason to taste. Place your Tomatoes and onions over the top of the fish.Dirzzle some olive oil over the top if you like.bake until done, 25mins..Enjoy