I've just made myself one of my favourite dishes, dearly loved ever since I was a kid. It's easy enough to make, you need some lean tuna (even a can will work), some butter, some garlic and vinegar (preferably balsamic). Grind it all together into an evenly textured paste (even a bowl-and-fork combo works) then spread it on very good, fresh bread. Stale or nonbread stuff probably won't work, but poverty is no excuse for bad bread. Learn to bake for Chris' sakei, it's not that hard.
This dish, as exotic and weird as it may sound to you does in fact exist, of course, you probably know it as tuna salad. Except the fat (butter) is there replaced with mayonnaise, and the acid (vinegar) is replaced with either mustard, vinegar-based pickles or both. And the garlic is taken out seeing how lunch is usually in the middle of the work day and people don't want to garlic up their boss.
To me replacing the butter with mayo in this dish sounds gross, even if I'm not considering the awful stuff mayo mostly gets replaced with in turn, and think of actual hand made, egg and olive oil based mayo, and replacing the vinegar unappetizing at best. But then again it may be a cultural thing.
A remarkably mirrored situation exists with my all-time favourite entree, too. Deviled eggs, if properly made, take mayo and the sauce takes sour cream and mustard. The dish commonly eaten of course is egg salad, which takes some butter or oil instead of mayo, and some vinegar instead of mustard or sour cream. I never cared much for egg salad myself, and in certainly I wouldn't trade the mayo for butter in this just as I wouldn't have traded the butter for mayo in that.
The moral of all this being that the structure of the world is permanently the same, much like say the grammar of the language of our existence. The words used to fill the places grammar dictates vary however, and that variance yields different lives and different foods, these two not being quite as undivorced as one might superficially imagine.
You are what you eat, after all.———