In a large pot, warm the olive oil over medium-low heat. Add the diced onion, sprinkle with a pinch of salt and pepper, and cook for about 3 minutes, until translucent.
Next, add the garlic, bell peppers and dried herbs, and continue to cook for 5 more minutes. Pour in the can of diced tomatoes with their juices, tomato sauce, vegetable broth, water, and lentils, and stir everything together. Turn the heat to high to bring to a boil then reduce it to medium and cook for about 35 minutes, or until the lentils are tender.
Serve the soup warm with fresh parsley and add brown rice as desired on top of the soup.
Note that if you add all of the rice to the pot with the soup, the starches will cause it to thicken, almost like a stew. I recommend adding it as needed as you eat. Store leftovers in an airtight container in the refrigerator for up to 3 days.