A tatin is usually made of apples and puff pastry, which is a really old fashioned but such a tasty recipe. Served with a scoop of vanilla ice cream, I would not ask for anything else. My variation though will build a bridge between both, savory and sweet. Sometimes a little persuading is needed to try out things we not yet know.
I am always telling my kids: „you don´t have to eat what you don´t like but you got to give it a try first“.
As all of you know the gorgeous taste and smell of sautéed onions, the sweetness pared with onions is nothing to be too crazy. Sometimes it might be only the wording of a dish that keeps us from trying. For instance, if I would just serve you an onion tart with pear and blue cheese, things would have a different impact on your imagination. So what I want to say is, just give it a try and think of a dessert with savory notes or the opposite if you may. It is all about what you make of it.