In a small bowl, combine all the sauce ingredients. Set aside.
Divide the beef into 8 balls. Prepare a piece of parchment paper (about 8x8 inches).
Heat a cast-iron pan over medium-high heat until hot. Grease with a tiny bit of oil.
Place a beef ball in the pan, cover with the parchment, and press it down with a burger press or spatula until flat. Cook for 1-2 minutes undisturbed, then flip the patty. Season with salt and pepper and top with a slice of American cheese.
To assemble a burger, spread the sauce on both buns. Add the patty and any other toppings you want. Enjoy!