In a bowl, mix together mayo, ketchup, mustard, sweet relish, salt, pepper, and Worcestershire sauce until well combined. Adjust seasoning to taste. Set aside.
Heat your griddle to medium-high heat. Lay out the bacon slices on the griddle and cook until crispy. Remove and set aside. Using the bacon grease, cook the sliced onions until caramelized and golden brown. Remove and set aside.
Season the beef patties generously with AB's AP Rub and AB's Burger Rub on both sides. Place the seasoned patties on the hot griddle and cook to your preferred doneness, flipping once halfway through.
Spread a thin layer of mayonnaise on the inside of each pretzel bun. Place the buns on the griddle and toast until golden brown and crispy.
On the bottom half of each toasted pretzel bun, spread a generous amount of the prepared burger sauce. Place a cooked beef patty on top of the sauce. Add a layer of crispy bacon on top of the patty. Top the bacon with a handful of caramelized onions. Place another beef patty on top of the onions. Add another layer of bacon. Finish with the top half of the pretzel bun.
Serve your homemade Baconator straight from the griddle while it's hot and the flavors are at their best. Enjoy the irresistible combination of juicy beef, crispy bacon, and flavorful toppings!