Whisk together the 2 tbsp mayonnaise, 1 tbsp yellow mustard, 1 tbsp ketchup, 1 tsp pickle brine, 1/2 tsp garlic powder, and 1/2 tsp onion powder in a small bowl until smooth. Set aside.

Toast the buns cut-side down in a skillet over medium heat for about 2 minutes, until the cut surfaces are golden, then remove from heat.

Heat 1 tbsp vegetable oil in a cast iron skillet over high heat for 2 minutes until shimmering. Divide the 8 oz ground beef into 4 equal balls and season with 1 tsp kosher salt and 1/2 tsp black pepper. Working 2 at a time, place the beef balls in the pan and smash flat to about 1/4 inch thick. Cook undisturbed for 2 minutes.

Flip each patty and lay 1 slice of American cheese on top. Cook for 1 minute on medium heat until the cheese is melted, then stack 2 patties together for 15 seconds. Repeat with the second batch.

Spread the sauce on both bun halves. Layer 4 pickle chips, the diced onion, the double-stacked patty, 2 tomato slices, and a handful of shredded iceberg lettuce on the bottom bun. Press the top bun on and serve immediately.