Using your hands, form four even-sized patties with the ground beef; 6oz each. Season with salt and pepper and press the middle of each patty with your finger (they say indenting the burger meat will prevent it from shrinking when cooking; I think it works!)
Heat up a cast iron skillet over medium-high heat. Add your burgers and let cook, undisturbed, for 6 minutes. Flip and cook for 6 minutes more for medium to medium-rare. If adding cheese, top it over the burger after you flip it (but not if you're Whole30ing, silly!)
Prepare your lettuce leaves for each serving. I use 2-3 leaves depending on the size. If the leaves are big, 2 should suffice. What I usually do is create a wide lettuce bed by slightly overlapping the lettuce. Place the burger in the center and add your toppings. Wrap and fold the leaves around the burger and enjoy!