Clean and chop/dice the vegetables.
In a soup pot, pour oil and add the chopped vegetables except for the potatoes. The potatoes cook faster than the other vegetables, so they go into the pot later. Saute the vegetables until they develop the flavor, about 3-4 minutes.
Add water or chicken broth. Add tomato paste or tomato sauce and cubed potatoes. Simmer the soup until the vegetables are half cooked, about 10-15 minutes.
Meanwhile, place the ground meat, rice, egg, chopped onion, parsley, salt, and pepper in a bowl.
Mix everything to incorporate all the ingredients and make a paste. Set aside.
With wet hands, grab a dollop of the meat mixture and roll it between your palms to create a meatball. Keeping your hands wet, drop the meatballs into the soup.
Let the soup simmer for 10-15 minutes so the meatballs get cooked. Taste for salt.
Add two tablespoons of vinegar or lemon juice. Taste and add some more as you prefer.
Chop the parsley and sprinkle it over the soup.
Serve with a dollop of sour cream or plain yogurt and hot peppers.