Make the sauce. In a small bowl, whisk mayo, sugar-free ketchup, relish, mustard, vinegar, paprika, onion powder, garlic powder, salt, and pepper. Adjust tang with a splash more vinegar if needed. Chill while you cook.

Prep the toppings. Rinse and pat dry your lettuce. Slice pickles and finely mince the onion. Keep everything handy for quick assembly.

Portion the beef. Divide ground beef into 6 equal balls, about 4 ounces each. Keep them loose—don’t overwork. Season the tops lightly with salt and pepper.

Heat the skillet. Use a cast-iron or heavy stainless steel pan over medium-high to high heat. Add a light film of avocado oil, ghee, or tallow. You want it hot—just shy of smoking.

Smash the first batch. Place 2–3 beef balls in the pan, seasoned side down. Immediately smash with a sturdy spatula or burger press until very thin (about 1/4 inch). Season the exposed side with more salt and pepper.

Get the crust. Cook without moving for 60–90 seconds until the edges are very crispy and browned. Flip, top each patty with a slice of American cheese, and cook 30–45 seconds more until cheese melts.

Repeat. Transfer patties to a plate and cover loosely to keep warm. Repeat with remaining beef.

Assemble “Big Mac” style. Lay down two large lettuce leaves. Add a smear of sauce, a sprinkle of minced onion, and some chopped lettuce if you like. Place one cheesy patty, top with pickles, more sauce and onion, then stack the second patty. Cap with another lettuce leaf.

Serve immediately. Add extra sauce on the side and more pickles if you’re team tangy.