Preheat your Napoleon P500RSIB Gas Grill will all burners turned to high heat for about 20 minutes.
Form 1/4 lb portions of the beef into patties that are slightly larger in diameter than your burger bun.
Season the beef with Yoder Smokers Beef Rub.
Place the patties on the grill grates inside the preheated grill. Close the lid. At about 5 minutes (or when the burger patty releases easily from the grate) flip the burger, transferring it to a spot on the grill that has not had food on it already. This will make sure that the grates are as hot as possible. Close the lid and continue cooking.
Place your buns on the grill to toast. Remove when lightly toasted.
When the internal temperature reaches roughly 140ºF, place your cheese on the patties to melt. Close the grill and continue cooking until the internal temperature reaches 150º-155ºF.
To build the burger, spread the bottom bun with mayonnaise. Top with leaf lettuce, then a slice of tomato seasoned with salt and pepper. Add thin sliced onions (optionally- softened by massaging salt into the onion and letting it rest for 10 minutes). Top with the burger patty and cheese. Spread the top bun with ketchup and place the bun over the beef.