Clean out and wash the lentils. Then parboil them for 7min in enough water to cover them. Strain the lentils and repeat the parboiling for another 7min. Then wash, strain and set aside the parcooked lentils.
Meanwhile prepare the rest of the ingredients required. Chop the garlic, onions, carrots and celery. Chop the coriander but keep the stem and the leaves separated.
Heat the olive oil in a large casserole and sauté the garlic and onion until they soften. Then add the cumin and coriander stems only, mixing well until they become fragrant.
Continue by adding the tomato paste and passata and let them cook with the rest of the ingredients for a few minutes. Then add the strained lentils, carrots, celery, salt and the 2L boiling water. Bring it all to a boil and then reduce the heat to medium allowing the soup to cook for 25-30min.
Once you turn it off add the red wine vinegar and the fresh coriander leaves. Serve warm with some crusty bread or homemade dried bread rusks and olives.