Animal Style Burgers

• 2 Tbsp vegetable oil, plus more for brushing
• 2 large onions, finely chopped
• Kosher salt
• 1/4 cup mayo
• 2 Tbsp ketchup
• 1 Tbsp sweet pickle relish
• 1/2 tsp white vinegar
• 2 lbs 80/20 or 85/15 burger
• 4 large burger buns
• 1/4 cup sliced dill pickles
• 3/4 cup shredded iceberg lettuce
• 4 to 8 thin slices tomato
• fresh ground pepper
• 1/4 cup yellow mustard
• 8 slices real American cheese

Heat vegetable oil in a skillet over medium-low heat. Add onion, 3/4 tsp salt, cover and cook until golden and soft, about 30 minutes. (if the onions brown too quickly, reduce the heat to low.) Uncover, increase the heat to medium high and continue to cook, stirring often, until caramelized, about 8 more minutes. Add 1/2 cup water to the skillet, scraping up any browned bits from the bottom of the pan. Simmer, stirring, until the water evaporates, about 2 more minutes; transfer to a bowl and set aside. (The onions ca be made up to 3 days ahead; cover and refrigerate, then reheat before using.)

Mix the mayo, ketchup, relish and vinegar in a bowl; set aside. Shape the beef into 8 patties, about 4 inches wide and 1/2 in thick.

Preheat the grill.

Toast the buns under a broiler in the oven, or in a toaster oven. Spread each toasted bun bottom with about 1 Tbsp of the mayo mixture, then top with a few pickles, lettuce, 1 or 2 slices tomato and more mayo mixture, then set aside.

Season both sides of the patties with salt and pepper. Place a sheet of foil on the grates and lightly brush with vegetable oil. Cook the patties on the foil for 3 minutes, spread 1-1/2 tsp mustard on the uncooked side of each patty, then flip and top each with 1 slice cheese; continue cooking about 2 more minutes for medium doneness. Top 4 of the patties with caramelized onions, then cover with the remaining patties, cheese-side up. Sandwich the double patties on the buns.