I've thought of this in the past too, a dream more than anything.
I'd call it Toast and that's all I'd sell, different types of bread, toasted with different things on top. There must be a standard 15/20 things people eat on toast with say 5 different types of bread, maybe do specials like crumpets or muffins, nothing too fancy though.
Tell me it's not a winner, how many people have you ever met who don't like toast?