Heat the margarine and sauté the finely chopped onion. Drain and add the corn. Pour the tomatoes on top, stir and bring to the boil. Pour in the rice, add a little water and simmer on a low flame until the rice is cooked through.
If the soup is too thick, add a little more water. Season with salt and carefully stir in the cheese. The cheese can be streaked, diced or grated. The tomato soup is ready when the cheese starts to melt.
It goes well with fresh baguette or, if you like it, you can also add croutons.