Divide the ground beef into 4 equal portions (about 6 oz each). Gently form each portion into a round patty approximately 3/4 inch thick, handling the meat as little as possible to avoid toughening it.

Use your thumb to press a shallow dimple into the center of each patty. This prevents the burger from puffing up during cooking and ensures an even cook.

Season both sides of each patty generously with kosher salt, black pepper, and garlic powder (if using) right before cooking — do not season in advance.

Heat a large cast-iron skillet or griddle over medium heat. Add butter and let it melt. Place buns cut-side down and toast for 30–60 seconds until golden brown. Remove and set aside.

For stovetop: Increase heat to medium-high. Add avocado oil to the skillet and let it get very hot. Add the patties and cook undisturbed for 3–4 minutes until a deep brown crust forms on the bottom.

Flip the patties once. Cook an additional 2–3 minutes for medium (150–155°F internal), or 3–4 minutes for well-done (160°F). Do not press down on the patties with your spatula.

For grill: Preheat grill to medium-high (400–450°F). Oil the grates lightly. Grill patties 3–4 minutes per side over direct heat with the lid closed.

In the last 60 seconds of cooking, place one slice of cheese on each patty. Cover the pan with a lid or tent loosely with foil to trap steam and melt the cheese completely.

Remove patties from heat and let them rest for 2 minutes before assembling.

Spread mayonnaise on the bottom bun, then layer lettuce, the cheese-topped patty, tomato, onion, and pickles. Add mustard and ketchup to the top bun. Press together gently and serve immediately.