Form ground beef into 8 equal-size balls. Put between 2 pieces of parchment paper or wax paper. Using a small saucepan or pot, flatten burgers by pressing down, forming ¼-inch patties. Season with salt and pepper.
Allow 2 large skillets (preferably cast iron) or a griddle to get very hot. Place burgers in pans and cook for 2−3 minutes on each side. These will be medium to medium well and should have a caramelized crust.
Top each patty with a slice of American cheese and remove from pans or griddle.
Prepare buns with 1 tablespoon signature sauce on top and bottom of each bun. Place 4−5 pickled onions on the bottom bun. After removing burgers from the pans, stack 2 burgers together and place on bottom bun. Finish with top bun and serve immediately.
Mix all ingredients evenly.
Pickled White Onions
Place onions in a heatproof bowl. Combine all ingredients except onions in a pot and bring to a boil.
Remove from heat and pour liquid over onions. Allow to cool. Refrigerate.