Preheat your oven to 400°F (190°C) or preheat the air fryer according to the manufacturer's instructions.

In a large mixing bowl, combine the ground beef, onion powder, garlic powder, diced onion, Worcestershire sauce, sweet relish, salt, and pepper. Mix until well combined.

Take a small portion of the beef mixture and flatten it in your hand. Place a cheddar cheese cube in the center and carefully form the beef mixture around it, shaping it into a meatball.

Repeat the process with the remaining beef mixture and cheese cubes.

If baking, place the meatballs on a baking sheet lined with parchment paper. If air frying, place the meatballs in the air fryer basket, making sure they are not overcrowded.

Bake in the preheated oven for 15-20 minutes, or air fry at 375°F (190°C) for 10-12 minutes, until the meatballs are cooked through and golden brown.

While the meatballs are in the oven, work on your sauce and bowl ingredients.

Combine the mayonnaise, ketchup, yellow mustard, sweet relish, vinegar, and Worcestershire sauce in a small bowl. Mix well until all ingredients are thoroughly combined and the sauce is smooth.

Taste and adjust the seasoning if necessary. You can add more mustard for tanginess or more sweet relish for sweetness, according to your preference. If you want it to be thinner, add a splash of water and then adjust the seasoning to taste. Set aside.

Arrange a bed of green leaf or romaine lettuce and add tomatoes, pickles, and diced red onion. Top with the meatballs and a generous portion of sauce.