Heat olive oil in a large soup pot over medium-high heat. Now, sauté the onion for about 3 minutes, until translucent.
Then, cook the carrots, celery, bell pepper, rosemary sprig, and bay leaf for about 4 minutes more, adding a few tablespoons of water to prevent food from burning.
Add garlic and continue sautéing for 1 minute more, until aromatic. Add Swiss chard leaves and canned tomatoes to the pot. Pour in 2 cups of water (or vegetable broth if you prefer) and let it cook for 15 minutes more.
Add the other ingredients and stir to combine. Continue to cook, partially covered, for 10 minutes more, until cooked through. Bon appétit!