Wash, clean and slice the zucchini. Clean, wash and cut the peppers into wide strips. Peel onions and cut vegetable onion into rings. Cut the remaining onion into fine cubes.
Dab tomatoes dry. Knead minced meat, diced onion, tomato paste and Italian herbs. Season with salt and pepper and form into 4 flat meatballs. Grill the meatballs on the hot grill for about 15 minutes.
Add the vegetables after about 5 minutes. If necessary, place the vegetables in a grill tray, thereby doubling the grilling time approx. Remove meat and vegetables from the grill and keep warm. Place the bread roll halves on the grill for 3 minutes, turning them over.
Cover with salad cream, meat, vegetables and ketchup.