Preheat grill to high heat (450–500°F). Place a cast iron skillet or flat-top griddle on the grill to heat.
Divide beef into 8 loose meat balls (about 2 oz each). Do not pack tightly.
Place a beef ball onto the hot surface. Using a heavy spatula or burger press, smash firmly until about ¼ inch thick. Hold for 10 seconds.
Season with salt and pepper. Cook for 2 minutes until edges are brown and crispy.
Flip, add cheese, and cook for 1 more minute until melted.
While burgers cook, butter the buns and toast lightly on the grill.
Assemble burgers by spreading sauce on buns, adding patties (double stack for classic smash burgers), and topping with your choice of lettuce, tomato, pickles, or onions.
Serve immediately and enjoy!