Make the burger sauce: In a small bowl, mix 1/3 cup mayo, 1.5 tablespoons ketchup, 1 teaspoon yellow mustard, and 1 to 2 teaspoons pickle juice. Add a pinch of garlic powder and black pepper. Stir and chill.

Portion the beef: Divide the ground beef into 8 to 10 loose balls, about 2 ounces each. Don’t pack them tight; loose balls smash and crisp better.

Preheat the pan: Heat a large cast-iron skillet or griddle over medium-high until very hot. Add a light film of oil.

Season smartly: Sprinkle one side of each beef ball with salt and pepper. You’ll season again after the flip if needed.

Smash onto the skillet: Place 2 to 3 beef balls in the pan, seasoned side down. Immediately smash each one very thin—about 1/8 inch—using a sturdy spatula or burger press. Press for 10 to 15 seconds to lock in that crust.

Top with onion: Scatter a little diced onion over each patty while it sears. Let the patties cook undisturbed for 1.5 to 2 minutes until the edges are deeply browned and crisp.

Flip and cheese: Scrape under each patty to release the crust and flip. Add a piece of cheese to each. Cook 30 to 45 seconds more, just to melt.

Fuse with tortillas: Place a tortilla directly on top of each cheesy patty, then press gently so the cheese sticks to the tortilla. After 15 to 20 seconds, use the spatula to lift the tortilla and patty together and flip so the tortilla hits the pan for about 10 to 15 seconds. This warms and softens it.

Repeat: Move finished taco bases to a plate and keep warm under a clean towel. Repeat with remaining beef and tortillas, adding a touch more oil if the pan looks dry.

Assemble: Spread a little burger sauce on the meat side. Add shredded lettuce, pickles, onions, and tomato if using. Fold and serve immediately while hot and crispy at the edges.