Preheat your oven to 400 degrees F. While that's warming up, start on your beef. Cook the ground beef and diced onion in a large skillet over medium heat. Season with salt, pepper, garlic powder and onion powder. Cook until the beef is browned and the onions are translucent. Drain excess grease. 

Add 2/3 cup of your Homeamde Big Mac sauce into the ground beef mixture. This will give it more flavor and add creaminess to the hamburger casserole.

Transfer the beef and onion mixture into a baking dish, spreading it out to form the base of your casserole dish.

Sprinkle the shredded cheddar cheese all over. Then arrange a layer of tater tots on top. This layer not only adds a delightful crunch but also a heartiness that fills you up.

Slide the dish into the oven and bake for about 40-45 minutes, or until the tater tots are golden brown and crispy.

Once out of the oven, let the casserole cool for a moment, then add shredded lettuce, diced dill pickles, and diced tomatoes on top of the casserole for that juicy, fresh element. Drizzle with remaining homemade Big Mac sauce right before serving.

Finish the dish off with a sprinkle of sesame seeds to mimic the bun flavors.