Cut meat in small pieces. In a large skillet, sear in vegetable oil until a reddish-brown crust appears. Add sliced onions and quartered tomatoes. Saute them well, then add diced carrots and potatoes. Transfer meat and vegetables to soup kettle with water, bring to a boil. Add rice, diced potatoes and cook about 20 minutes. In the final 5-10 minutes add salt and spices. To serve, top with yoghurt or sour cream, garnish with choppped greens.