Caramelize the onions

• Slice the yellow onion thinly.
• Spread the slices on a hot, greased grill and season with a pinch of salt and sugar.
• Cook until golden and caramelized, turning occasionally.

Add the cheese

• Place a slice of cheese on half of the caramelized onion pieces so they melt.

Grill the patties

• Shape the ground beef into thin patties and season with salt and pepper.
• Grill the patties, optionally spreading a little mustard on them while they cook.
• Flip and cook through.

Stack the Flying Dutchman

• Layer the patties with the cheese-topped onion pieces, using the onions as the buns.
• Top with the remaining onion pieces to close the burger.

Serve

• Enjoy with special sauce and pepperoncini on the side.