Prepare the tomatoes and potatoes. If you’re not cooking the soup right away, keep the potatoes in a bowl of cold water to prevent them from oxidizing.

Heat oil in a medium soup pot over medium-high heat, and add the tomatoes. Cook for 3-5 minutes, until tomatoes have softened.

Add the water and potato, and bring to a boil over high heat. Once boiling, cover, reduce the heat to medium, and cook for 15 minutes.

Finally, add the scallion and salt to taste. Serve hot or at room temperature!