1Pre-heat grill to med-high.
Take the large zucchini and slice into 1/4 inch rounds. Do the same with the onion and tomato
2On a platter place zucchini rounds and brush with olive oil on both sides. Sprinkle a little of the garlic herb rub on both sides of zucchini and onion rounds. Brush onion round also.
3I use a veggie grate on the grill. Place zucchini and onion rounds on great. Grill for about5-7 minutes per side. Brush hamburger buns with a little butter and grill till just toasted.
Once zucchini and onions have been grilled. Sprinkle a little parmesan cheese on both sides of zucchini and onions. Place a zucchini round then onion then sliced tomato on to buns top with a little more cheese. top with other hamburger bun. Serve warm and enjoy..