Smash burger with cheesy onion bake

I was looking for a cheesy onion recipe and found Tennessee Onions. Basically onions, butter, and cheese, then baked. Nothing wrong with that, so I put some on this week’s burger. It had Home ground chuck and sirloin smash patties, American, cheesy onion bake, crispy prosciutto, and my burger sauce, on a buttered and griddled homemade brioche-style bun