200g pickled cherry peppers, seeds and stems removed, roughly chopped
450g sliced bacon, divided
570g freshly ground beef, divided into four 5-ounce patties
Kosher salt and freshly ground black pepper
4 thick slices yellow or white onion
4 slices American or cheddar cheese
Shredded iceberg lettuce and pickles (if desired)
4 toasted hamburger buns
Adjust oven rack to middle position and preheat oven to 205°C. Arrange half of bacon on a rimmed baking sheet and cook in oven until crisp and well browned, about 15 minutes. Drain on paper towels.
2. Meanwhile, place cherry peppers in the work bowl or a food processor. Pulse until finely chopped, 8 to 10 short pulses. Cut remaining half of bacon into 1.25cm pieces. Heat bacon in a 30cm non-stick or cast iron skillet over medium heat. Cook, stirring, until crisp, about 8 minutes. Add sugar and chopped cherry peppers and their juices. Cook until juices are mostly evaporated and pepper-bacon mixture has a chunky, relish-like texture, about 8 minutes. Transfer to a bowl and set aside.
3.When ready to serve, season burger patties generously with salt and pepper and cook burgers to desired doneness on a hot grill or in a skillet on the stovetop, 50°C for medium rare or 60°C for medium, topping with cheese for last minute of cooking. Let burger patties rest for 5 minutes off heat. While burgers are resting, season onions with salt and pepper and cook on hot grill or in a lightly oiled skillet until tender and well browned on both sides.
4.Place shredded lettuce on bottom buns and top with burger patties. Top with bacon-cherry pepper relish, cooked onion slices, and bacon. Close burgers and serve immediately.