Chop cabbage, carrot, and string beans into very small pieces.
Chop tomato in small pieces and remove the seeds. Set aside.
Boil the corn in about 1 ½ cups of water until the corn is soft. Remove ¼ cup of corn and set aside.
Blend the rest of the corn into a paste and strain.
Mix the cornstarch with ¼ cup of water and set aside.
Heat the oil in a saucepan. Test the heat by adding one cumin seed to the oil; if seed cracks right away oil is ready.
Now add the cumin seeds. After the cumin seeds crack, add the carrot, cabbage, beans and ¼ cup of water. Cook the vegetables on medium heat until they are tender.
Next, add the corn paste, corn, cornstarch mixture, and two cups of water to the vegetables. Bring the soup to a boil add tomatoes and lower the heat to medium low. Let the soup cook for another five minutes. Add the lemon juice and serve.