Chop the veggies: Peel the carrots and potatoes and cut them lengthwise in half. Cut everything into bite-sized pieces.
Make the soup base: Finely chop the onion and sun-dried tomatoes, then sauté them in a large pot with oil from the sun-dried tomatoes for 2-3 minutes until softened.
Sauté the veggies: Add carrots, celery, and potatoes to the pot. Stir to coat and cook for 5-10 minutes while prepping the cabbage.
Chop the savoy cabbage: Cut the cabbage in half and remove the white core. Remove tough veins from the outer leaves and cut them into strips. Then, chop everything into bite-sized pieces.
Make the soup: Add vegetable broth, canned tomatoes, cabbage, red pepper flakes (optional), and a bay leaf. Give it a good stir, cover the pot with a lid, and simmer for 30-35 minutes.
Adjust seasoning with salt (depending on how salty your vegetable broth is). Serve with a little oil from the sun-dried tomatoes.
Notes
Use fire-roasted canned tomatoes instead of diced tomatoes if you want a smokier soup.
Stir in a can of cannellini beans or some TVP (textured vegetable protein) for an extra dose of plant-based protein to make to cabbage soup even more filling.
Serve the soup with some of the sun-dried tomato oil for a stunning presentation.
You can store this tomato and cabbage soup in airtight containers for up to 4 days in the refrigerator and up to 3 months in the freezer.