Finely chop the onion and garlic. Roughly chop the red pepper and carrot. Peel, then chop the sweet potatoes.
Heat the oil in a large pot, then gently sauté the onion for 5 minutes. Add the garlic and oregano and cook for another minute.
Add the chopped vegetables, spices and the tomato purée.
Stir for about a minute, then add the stock and bring to the boil.
Cover and cook for 25 minutes.
When the veggies are tender, add the coriander leaves. Using a stick blender, whiz the soup until you get a smooth, silky texture.