Cook the elbow macaroni according to package directions until just al dente. Drain thoroughly and set aside.

In a large skillet over medium-high heat, brown the ground beef with diced onions until the meat is completely cooked and the onions turn translucent and fragrant, about 6-8 minutes. Drain excess fat and season with salt and pepper.

In a medium bowl, whisk together mayonnaise, ketchup, mustard, pickle relish, vinegar, garlic powder, and onion powder until smooth and creamy.

Preheat oven to 350°F and grease a 9x13-inch baking dish. Layer half the cooked pasta on the bottom, followed by the beef mixture, then half the cheese. Dollop the special sauce evenly over the cheese. Add the remaining pasta and top with remaining cheese.

Bake for 12-15 minutes until the cheese melts completely and the edges start to bubble gently. Remove from oven and immediately top with fresh lettuce, diced tomatoes, and chopped pickles.