Put rice in boiling salted water and let it swell for about 20 minutes. Meanwhile peel and wash the carrots and potatoes and cut them into small pieces. Wash the tomatoes, cut 2 pieces into slices. Heat olive oil. Brown carrots, potatoes and tomato slices in it. Season with salt and pepper. Fill up with broth and cook covered for about 20 minutes.
In the meantime cut the rest of the tomato into quarters and remove seeds. Cut the flesh into small cubes. Clean and wash the spring onion and cut into fine rings. Puree the soup with the chopping stick. Season to taste with salt, pepper and vinegar. Add tomato cubes, spring onion rings and rice and serve