Make the sauce. In a bowl, whisk mayo, sugar-free ketchup, relish, mustard, vinegar, paprika, onion powder, garlic powder, and a pinch of sweetener. Season with salt and pepper. Chill while you prep the burgers so it thickens and the flavors meld.

Prep the toppings. Finely mince the onion, shred the lettuce, and slice the pickles. Keep everything cold for that crisp bite.

Portion the beef. Divide ground beef into 8 equal balls (about 3 ounces each). Keep them loose; don’t pack them tight.

Heat the skillet. Set a cast-iron skillet or heavy griddle over medium-high to high heat. Add a light film of avocado oil or ghee.

Smash the patties. Place 2–3 beef balls on the hot surface, leaving space. Immediately smash each ball flat using a sturdy spatula or a burger press covered with parchment. Aim for thin patties with wispy edges.

Season and sear. Sprinkle with salt and pepper. Cook 60–90 seconds until the edges are deeply browned.

Flip and cheese. Flip the patties. Top half of them with cheese. Cook another 30–60 seconds until cheese melts and the patties are cooked through.

Stack them. Place a plain patty on top of a cheesy patty to make double-stacks. Repeat with remaining patties.

Assemble. On a plate or in a shallow bowl, add a bed of shredded lettuce. Spoon on a generous layer of special sauce. Set the double-stacked patties on top. Add minced onions and pickle slices. Sprinkle with sesame seeds if you like that “Big Mac” look.

Optional bun. If you prefer a handheld version, use low-carb buns or chaffles. Layer sauce on both sides, add lettuce, pickles, onions, and the double-stacked patties.