Soak bread in water. Peel 1 onion and chop very finely. Squeeze the bread. Knead minced meat, egg, mustard, onion and bread. Season with salt and pepper. Form 4 very flat meatballs from the minced mass. Heat the oil in a large pan and fry the meatballs for about 3 minutes on each side.
Drain the cucumber salad in a sieve. Peel 2 onions and cut into rings. Clean, wash and drain the salad well. Wash, clean and slice the tomatoes. Cut open the buns. Heat a pan without fat, put the bread roll halves in it with the cut surface facing down, roast for about 1 minute, take them out
Spread mayonnaise on the halves of the rolls, layer lettuce, meatballs, tomatoes, cucumber, onions and barbecue sauce on the undersides of the rolls. Place the upper halves of the rolls on top and