3 bacon cheddar burgers caramelized Recipes

extra-virgin olive oil, onions (2 large), sliced into 1/2-inch-thick rings, salt and freshly ground black pepper, seasoned rice vinegar, sliced bacon , frozen 1 hour, ground beef chuck, worcestershire sauce, salt, freshly ground black pepper, unsalted butter, melted, extra-sharp cheddar, hamburger buns or alternatives such as kaiser or brioche rolls, sliced tomato, soft-leaf lettuce leaves or baby arugula

barbecue sauce, divided, ground beef, bacon strips, halved, sweet onion, sliced, butter, divided, hamburger buns, split, cheddar cheese