Gather your equipment: a cast-iron skillet, a spatula, and a meat thermometer. Preheat the skillet over medium-high heat until it’s just starting to shimmer, around 200°C/390°F.
In a bowl, gently mix the ground beef with salt and pepper, taking care not to overwork the meat to keep the patties tender. Form four equal-sized patties, each about ¾ inch thick, handling the meat lightly.
Place the patties carefully onto the hot skillet, listening for a satisfying sizzle. Let them cook undisturbed for about 3-4 minutes until the bottom develops a deep golden-brown crust.
Flip the burgers using a spatula, and cook for another 3-4 minutes on the second side, aiming for an internal temperature of 70°C/160°F for safety and juiciness. Add a slice of cheddar on top during the last minute to melt.
Meanwhile, thinly slice the onion and cook it in a separate pan with a tablespoon of oil over medium heat, stirring occasionally until sweet, golden, and caramelized—about 10 minutes.
While the burgers rest for 2 minutes off the heat, lightly toast the buns in the skillet with a little oil until golden brown and crisp.
Assemble your burger by spreading the bottom bun with some caramelized onions, then layering with lettuce, tomato slices, and pickles. Place the cooked patty with melted cheese on top, then add the top bun.
Serve your burger immediately, enjoying the crispy exterior, juicy interior, and balanced toppings that make every bite satisfying.
