Slice the large yellow onion into 1/2-inch thick rounds. In a large skillet, heat 2 tablespoons of olive oil over medium-low heat, then add the onion rounds. Drizzle with 1 tablespoon of Worcestershire sauce, sprinkle with 1/2 teaspoon of Creole seasoning, and 1/2 teaspoon of brown sugar. Cook for about 20 minutes, turning occasionally, until the onions are deeply browned and caramelized.

While the onions are caramelizing, season 12 ounces of ground beef with the remaining Creole seasoning. Form the beef into thin patties. Heat a separate skillet over high heat and, when hot, place the patties in the pan. Sear them for 2-3 minutes on each side until cooked through and nicely browned. In the last minute of cooking, place a slice of American cheese on each patty, allowing it to melt.

In a mixing bowl, whisk together 1/2 cup of mayonnaise, 2 tablespoons of relish, and 1 tablespoon of Dijon mustard until smooth. Incorporate 1 teaspoon of sugar, 1 teaspoon of garlic powder, 1 teaspoon of onion powder, 1 teaspoon of smoked paprika, and a pinch of cayenne pepper for heat. Stir until all ingredients are well combined for a flavorful sauce that will complement the Flying Dutchman Burger.

To assemble your Flying Dutchman Burger, start by placing one caramelized onion round on a plate. Add a cheesy beef patty on top, followed by a generous spoonful of your prepared sauce. Finish with another onion round to create a 'bun' effect. Repeat this assembly for all servings, serving immediately with extra sauce on the side for dipping.