Divide the ground beef into 4 equal portions. Shape each portion into a patty that's slightly larger than your buns.
Season both sides of each patty generously with salt and black pepper.
Place the patties on the grill or skillet. Cook for about 5 minutes on each side for medium doneness.
Add a slice of cheese to each patty during the last minute of cooking, allowing it to melt.
Toast the hamburger buns on the grill or skillet until lightly golden.
Assemble the burgers by placing a lettuce leaf on the bottom half of each bun, followed by a slice of tomato, a slice of onion, the cheese-topped patty, and any condiments of your choice.
Cover with the top half of the bun and serve immediately.