01 -
Slice the yellow onion into 4 large rings, keeping each ring intact. Season both sides with salt and black pepper.
02 -
Combine mayonnaise, ketchup, yellow mustard, apple cider vinegar, sweet relish, smoked paprika, garlic powder, and black pepper in a bowl. Mix thoroughly until fully incorporated.
03 -
Heat a griddle to medium-high. Place onion slices on the griddle and cook for 4-5 minutes per side until charred. Add a splash of water, cover, and steam for 3-4 minutes until softened.
04 -
Divide ground beef into 4 portions of ΒΌ lb each. Smash each into a thin patty using a burger press or spatula. Season both sides with burger seasoning.
05 -
Place patties on the hot griddle and cook for 3-4 minutes. Flip, then immediately add one slice of American cheese to each patty to melt.
06 -
With onions soft, place 4 slices mozzarella cheese directly on the griddle over medium heat. Once cheese starts to melt, put each cooked onion ring on a slice of mozzarella. Cook for 2 minutes until cheese is golden and toasted, then remove.
07 -
Layer the burger starting with the mozzarella onion base, add a generous spread of burger sauce, place burger patties with melted American cheese, add more sauce, and top with another mozzarella onion ring.