Preheat a Blackstone griddle by setting two burners to high and two to medium and allow it to heat for about ten minutes.

Mix ketchup, mayonnaise, mustard and chopped pickle in a bowl to make the sauce. In a separate bowl stir together garlic powder, onion powder, salt and pepper.

Form the ground beef into eight loose balls without pressing too tightly.

Brush butter on the medium heat side of the griddle and toast the buns cut side down until lightly golden then keep warm.

Brush butter on the high heat side and add the diced onions. Cook while stirring until lightly browned then divide the onions into four small piles.

Place a beef ball on each onion pile and press down firmly with a spatula or burger press until the patties are thin.

Season with half of the seasoning mix and cook undisturbed until the edges crisp. Flip the patties and season the other side.

Place a slice of Tillamook Cheddar or Cabot Cheddar on the plain patties so it melts while the meat cooks.

Spread the sauce on the toasted buns. Stack one onion patty and one plain patty on each bun and add tomato, lettuce and any extra onions from the griddle.