My Aunt Morey used a stovetop oven, on top of one of the burners of her kerosene fueled stove. She made absolutely fabulous cakes and other baked goods with it!

A modern-day version of the same thing is made by Coleman. (Amazon sells it for about $30.) It's made to work on top of their propane stoves, but I don't see any reason why it wouldn't work just as well on top of a gas burner stove.