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Heat the oil in a large pot over medium heat. Add the onion and sauté for 3-4 minutes. When the onions are cooked well, add the cabbage, carrots and tomatoes. Let cook for 2-3 minutes, stirring occasionally.
Meanwhile, cut the tofu into bite-sized pieces. Add the tofu and the remaining ingredients to the pot.
Turn up the heat and bring the soup to a boil, then turn to low and cover the pot. Allow to simmer for for 20 minutes, stirring occasionally.
Serve hot and add fresh pepper to each serving.