Heat the olive oil in a large saucepan, add the onion and sauté for about 5 minutes.
Add the carrots and sauté for a further 2 – 3 minutes.
Add the green lentils, tomatoes, dried oregano and stock, bring to the boil, then turn down and allow to simmer gently for 40 minutes. Stir occasionally.
Allow to cool a little then, blitz with a stick blender or in a food processor.