- 1
Make the signature sauce by mixing mayonnaise, ketchup, Worcestershire sauce, and a pinch each of garlic powder and smoked paprika. Set aside.
- 2
Heat 1 tablespoon oil in a large cast iron skillet or flat-top pan over medium heat. Add sliced onions with a pinch of salt and cook, stirring occasionally, until golden brown and caramelized, about 15-20 minutes. Remove and keep warm.
- 3
Divide ground beef into 4 equal portions (about 3 oz each). Gently form into loose balls - don't overwork the meat. Season each ball generously with salt, pepper, garlic powder, and onion powder.
- 4
Heat the remaining oil in the same skillet over medium-high heat. Place 2 beef balls in the pan, then immediately smash each one with a spatula or burger press until very thin (about 1/4 inch thick). Cook for 2-3 minutes until crispy and well-browned on the bottom.
- 5
Flip the patties and immediately top each with a slice of American cheese. Cook for another 1-2 minutes. Remove and repeat with remaining beef balls and provolone cheese.
- 6
In the same pan, quickly sear the sliced steak for 1-2 minutes until just cooked through. Season with salt and pepper.
- 7
Toast the pretzel bun halves cut-side down in the pan until golden brown, about 1 minute.
- 8
Assemble the burgers: spread signature sauce on both bun halves. On the bottom bun, stack one American cheese patty, half the grilled onions, half the seared steak, one provolone patty, and top with the remaining onions and steak. Crown with the top bun and serve immediately.