Begin by preparing all your vegetables: peel and dice the onion, garlic, carrots, and sweet potato. Chop the celery and cabbage.
In a large pot or Dutch oven, heat the olive oil over medium heat. Add the onion and garlic, cooking for about 3-4 minutes until the onion is translucent.
Add the carrots and celery to the pot. Sauté for another 5 minutes, stirring occasionally.
Add the sweet potato, diced tomatoes (with juices), vegetable broth, thyme, oregano, black pepper, and salt. Stir well to combine.
Bring the mixture to a boil, then reduce the heat to low. Cover and let the soup simmer for about 25 minutes, or until the sweet potatoes are tender.
Finally, stir in the chopped cabbage and allow it to cook for an additional 5-10 minutes until wilted and tender. Adjust seasoning if necessary.
Serve hot, garnished with fresh parsley if desired.