In a separate pot, cook the rice according to the package instructions. Once cooked, set it aside.
In a large soup pot, heat the olive oil over medium heat. Add the chopped onion. Sauté for 2-3 minutes, or until the onion becomes translucent and fragrant.
Add the diced carrot, and diced celery and garlic to the pot. Stir and cook for another 5 minutes until the vegetables begin to soften. Then add in shredded cabbage cook for another 2 minutes. Continue stirring.
Pour in the vegetable broth, lemon juice, and add the diced tomatoes (with their juices) to the pot. Stir in the dried thyme, red pepper flakes, and dried Italian seasonings. Season with salt and black pepper to taste.
Bring the soup to a boil, then reduce the heat to low, cover, and let it simmer for about 20-25 minutes, or until the vegetables are tender.
Once the vegetables are tender, stir in the cooked rice. Allow the soup to simmer for an additional 5-10 minutes to heat the rice through.
Just before serving, stir in the vegan Parmesan cheese until it's well incorporated into the soup. Adjust the seasoning if needed.
Ladle the Vegan Parmesan Cabbage Rice Soup into bowls. Garnish with fresh parsley or basil if desired.