Wash the pork belly. Boil 1 litre of water and vinegar. Add meat and cucumber seasoning and cook for 1 1/2 hours at medium heat. Peel onions and cut into rings. Peel and wash carrots.
Add onions and carrots to the meat 5 minutes before the end of the cooking time. Cut the cucumbers into slices. Remove the carrots and meat, let the stock cool down and degrease. Soak gelatine in cold water.
Cut the meat into approx. 1 1/2 cm thick slices and halve. Cut carrots into slices with a waistband knife. Layer meat, carrots and cucumbers in a large mould. Warm up the stock. Squeeze the gelatine and dissolve in the stock.
Season to taste with salt and sugar. Pour the stock over the slices of meat and let it set, preferably overnight. Arrange the sour meat with lettuce and tomato on a plate. Garnish with parsley.
Fried potatoes taste good with it.