Divide the ground beef into four equal portions. Gently shape each portion into a ball, then flatten it into a patty about 3/4-inch thick. Make sure the patties are slightly wider than your buns, as they will shrink during cooking. Use your thumb to create a slight indentation in the center of each patty to prevent bulging.
In a small bowl, mix the salt, black pepper, and garlic powder. Generously season both sides of the beef patties with the mixture. It is best to season right before cooking to prevent the salt from drawing out too much moisture from the meat.
Heat a large cast-iron skillet or a grill over medium-high heat. You want the surface to be very hot so that it creates a nice crust on the meat. If using a skillet, you may add a tiny bit of oil, though the fat from the beef is usually sufficient.
Place the patties onto the hot surface. Cook for about 3 to 4 minutes without moving them to ensure a deep brown sear. Flip the patties over and cook for another 3 minutes. Avoid pressing down on the patties with a spatula, as this squeezes out the juices.
During the last minute of cooking, place a slice of cheddar cheese on top of each patty. If you are using a grill or skillet, you can cover it with a lid for 30 seconds to help the cheese melt perfectly over the edges of the meat.
Spread the softened butter on the cut sides of the brioche buns. Place them cut-side down on the grill or in a separate pan for about 1 minute until they are golden brown and toasted. This adds flavor and prevents the bun from getting soggy from the burger juices.
Place the bottom bun on a plate and add a layer of ketchup and mustard. Top with a lettuce leaf, then the cheesy beef patty. Add the tomato slice, red onion, and pickles. Place the top bun on and serve immediately while hot.