Finely chop the onion, garlic, ginger, turmeric and chilli if used.
Peel the other vegetables, then cut them into small chunks.
Heat the oil in a large pot and gently sauté the onion for 5 minutes. Add the turmeric, ginger, cumin seeds and chilli and stir for 2 minutes.
Add the chopped vegetables, oregano and tomato purée. Stir for a minute, then pour in the chopped tomatoes and stock.
Bring to the boil, cover and cook for 25 minutes. Add the roasted peppers and cook for 5 more minutes.
Add the fresh coriander and, using a stick blender, process the soup until thick and silky.
Add the drained lentils and more stock, if you think it’s too thick.
Warm it up if needed, then serve.