Divide the ground beef into 4 equal portions and gently form each into a loose ball. Lightly season the balls with salt and pepper on all sides.
Heat the cast-iron skillet or griddle over high heat until very hot, about 2-3 minutes, until a few drops of water vaporize on contact. Place the beef balls onto the hot surface, spacing them apart.
Using a spatula, firmly smash each beef ball down into a thin patty, about 1/4 inch thick. Continue pressing until the edges are frizzled and the surface appears evenly flattened. Cook for 2-3 minutes without moving, until the underside develops a deep golden-brown crust.
Flip the patties and cook for another 1-2 minutes, allowing the other side to brown and the juices to bubble at the edges. The patties should be crispy on the outside and tender inside.
Remove the cooked patties from the skillet and place them on buns or a plate. Optional: toast the buns briefly on the skillet until golden. Add toppings or cheese as desired before assembling the burgers.
Serve immediately, showcasing the crispy edges and juicy interior of the smashed burger.
