The secret of a good lentil soup is to be generous with the olive oil. This dish can serve as a main meal, accompanied by bread and olives.
Rinse the lentils, drain them and put them in a large pan with enough cold water to cover. Bring to the boil and boil for 3–4 minutes. Strain, discarding the liquid, and set the lentils aside.
Wipe the pan clean, heat the olive oil in it, then add the onion and sauté until translucent. Stir in the garlic, then, as soon as it becomes aromatic, return the lentils to the pan. Add the carrot, tomatoes, tomato purée and oregano. Stir in 1 litre hot water and a little pepper to taste.
Bring to the boil, then lower the heat, cover the pan and cook gently for 20–30 minutes until the lentils feel soft but have not begun to disintegrate. Add salt and the chopped herbs just before serving.