Preheat your oven to 400°F (200°C). Lightly grease a 9x13 inch casserole dish.

In a medium mixing bowl, whisk together all the ingredients for the Special Sauce: mayonnaise, dill pickle relish, ketchup, yellow mustard, white vinegar, onion powder, and paprika. Set aside.

In a large skillet over medium-high heat, cook the ground beef and diced yellow onion until the beef is browned and the onion is soft, about 8-10 minutes. Break up the beef as it cooks. Add the minced garlic and cook for one more minute until fragrant.

Drain off any excess grease from the skillet. Stir in the salt and black pepper. Remove from heat.

Add half of the prepared Special Sauce (about 1 cup) and 1 cup of the shredded cheddar cheese to the ground beef mixture. Stir until everything is well combined and the cheese begins to melt.

Spread the beef mixture evenly into the bottom of the prepared casserole dish. Arrange the frozen tater tots in a single, even layer over the top of the beef.

Bake for 20-25 minutes, or until the tater tots are golden brown and crispy.

Remove the casserole from the oven and sprinkle the remaining 1 cup of cheddar cheese over the hot tater tots. Return to the oven for 3-5 minutes, just until the cheese is completely melted and bubbly.

Let the casserole rest for 5-10 minutes before serving. This allows it to set up slightly.

To serve, top the casserole with shredded lettuce, diced pickles, diced white onion (if using), and sesame seeds. Drizzle the remaining Special Sauce over the top.