Delicious Smash Burgers

Combine ketchup, mayonnaise, pickle relish, vinegar, white sugar, and garlic in a small bowl. Adjust the seasoning to your liking with salt and black pepper; cover and set aside for later use.

Divide the ground beef into four equal portions. Shape each portion into a uniform ball and refrigerate until ready to cook.

Melt butter on the cut sides of hamburger buns. Heat a large skillet, preferably made of cast iron or nonstick material, over medium-high heat (you can add a small amount of vegetable oil if concerned about sticking).

Add two hamburger balls to the skillet. Flatten them using the bottom of a small sauce pot or a spatula, holding them in place until they're seared on the bottom for about 1 minute. Season with salt and pepper to taste. Continue cooking until a good crust forms, then flip the patties.

Once the patties are almost done, place a slice of cheese on top. Move the cooked burgers aside and cook the hamburger buns in the skillet, butter side down, until toasted. Continue cooking the burgers until the cheese is melted and the meat reaches your desired level of doneness, about 5 minutes. Use an instant-read thermometer to check that the internal temperature reaches at least 160 degrees F (70 degrees C).

Transfer the buns to a plate and top each one with a cooked patty. Spread some of the special sauce on the toasted side of the top bun.

Add a few slices of onion to each patty, cover with the top bun, and serve immediately.