01 -
Combine mayonnaise, ketchup, relish, apple cider vinegar, yellow mustard, Worcestershire sauce, and granulated sugar in a bowl. Whisk thoroughly until smooth. Cover and refrigerate until needed.
02 -
Mix ground beef with salt, black pepper, and garlic powder gently to avoid toughening the meat. Divide into eight equal portions and lightly flatten to about 12 mm thickness.
03 -
Sprinkle both sides of onion slices with salt and sugar. Heat olive oil in a skillet over medium-low heat and cook onions for 5 to 8 minutes per side until golden and tender but with crispy edges.
04 -
Increase heat to medium-high. Place patties in the skillet and cook 2 to 3 minutes per side, pressing down gently for even thickness. After flipping, top each patty with a cheese slice and cook until melted and patties are cooked through.
05 -
On a plate, place one caramelized onion slice, then a cheesy patty, followed by a generous dollop of the prepared sauce. Repeat layering with another patty and sauce. Crown with a final onion slice to complete the stack.