Soak the lentils in the beer for 3-4 hours. Cut the bacon into cubes and fry in a saucepan over medium heat. Cut the onion into cubes and add to the bacon and fry. Add the lentils with the beer, the hot water and the bay leaf. Bring to the boil and simmer for about 40 minutes.
Clean, wash and chop soup vegetables. Peel the potatoes and cut into cubes. Add the soup vegetables and potatoes to the lentils with the stock cubes approx. 10 minutes before the end of the cooking time. Drain the tomatoes a little, cut them into small pieces and add to the soup. Season everything well with salt, pepper and vinegar.