1. Heat a pan with olive oil to medium heat.
2. Add diced onions, coating them evenly in oil. If the pan seems dry, add more oil or a splash of water. Cover and let onions cook down for 30 minutes, checking on them regularly to make sure they are caramelizing and not burning. They are ready when they are nicely browned and soft, and cooked down to about a third of their original size.
3. Add chopped garlic and sautée for 1-2 minutes. Add chopped veggies (if using) and sautée with garlic for an additional 1-2 minutes.
4. Add your spices and cook for a few minutes until very fragrant, but not burnt.
5. Add diced or pureed tomatoes, split red lentil (if using) and parsley or basil (if using), stirring well.
6. Cook down tomatoes until they bind with the onions, forming a nice paste and the lentils are fully cooked (20-30 minutes). At this point, you can add more water for a thinner sauce.