1. Preheat grill to 550 degrees F with flat top cast iron griddle on top of the grill grates.
2. Divided ground beef into 8 equal chunks and form into balls. Don’t overwork the beef.
3. Once the flat top griddle is hot, place a three-finger pinch of onion slices in a cluster on the griddle. Season with Weber Gourmet Burger seasoning. Then place one rolled ball of ground beef in the middle of the onions. Using a burger press. or wide metal spatula, smash the burger ball down into the onions until very flat. Season again with Weber Gourmet Burger seasoning and flip when crispy.
4. With the cooked onions now facing up, place a slice of cheese on top and let it melt. Once cooked a melted, remove from griddle and repeat with the rest of the onions and burger balls.
5. Enjoy with your favorite toppings and sauces!