@tinyfaery I never thought about it that way, but that totally makes sense. A lot of the classic dishes we have today probably started as peasant foods. I just looked that up, and there are a couple very familiar things on there, like soul food, minestrone soup, and pot-au-feu (stew.) Most of our ancestors were probably poor farmers who cooked with whatever was on hand.
There are a couple recipes based on stale bread, like panzanella, French onion soup, and bread pudding. The peasant food thing might also be why other cultures have foods that seem strange to us. I just read an article about a Laotian restaurant in my city that serves ant egg salad. Burmese balachaung is a more familiar dish from readily-available ingredients. It’s made from dried shrimp, onions, and red pepper flakes. It’s dry, so it basically lasts forever, and it has a strong flavor, so a little goes a long way. Sprinkle a tiny bit over rice and it makes a satisfying meal.
Spices were really expensive back in the day, especially for people in Europe who had to get them from Asia. You can grow onions in your back yard. So I guess it makes sense that people would use onions.