01 - Melt butter in a large skillet over medium heat. Add sliced onions, sugar, and salt. Cook for 20–25 minutes, stirring occasionally, until golden brown and caramelized. Add a splash of water if needed to prevent sticking. Remove from heat and set aside.
02 - Combine ground beef, kosher salt, black pepper, and Worcestershire sauce in a large bowl. Gently mix until incorporated, being careful not to overwork the meat. Shape into 4 equal patties, pressing a slight indentation into the center of each to ensure even cooking.
03 - Preheat grill, grill pan, or skillet to medium-high heat. Place patties on the cooking surface and cook for 3–4 minutes per side for medium doneness, adjusting time to reach desired doneness. If adding cheese, place a slice on each patty during the final minute and cover to melt.
04 - While burgers are cooking, place bun halves cut side down on the grill or in a dry skillet. Toast until golden brown and lightly crisp, approximately 1–2 minutes.
05 - Layer lettuce and tomato slices on the bottom bun. Place the cooked patty on top, followed by caramelized onions and pickles. Add condiments as preferred. Cover with the top bun and serve immediately.