Sour lentil soup by Yotam Ottolenghi.

- How to make soups with real flavour and texture | Yotam Ottolenghi | Food | The Guardian
Adas bil hamoud (aka sour lentil soup)
Versions of this soup, in which lemon is king, are found all over the Arab world.
Mine is ever-changing, depending on what kind of stock I have in my freezer, or herbs in my fridge, so feel free to play around with the ingredients as you see fit.
I like my soup super lemony, but adjust this to your taste, too.
If using vegetable stock, consider adding a couple of teaspoons of miso paste to enrich the broth.
Prep 25 min
Cook 1 hr
Serves 4-6

200g brown or green lentils
110ml olive oil
2 large onions, peeled and finely chopped
5 large garlic cloves, peeled and crushed
1½ tbsp cumin seeds
3 lemons – finely shave the skin off 1 into 5 wide strips, then juice all 3 to get 75ml
Salt and black pepper
3 firm, waxy potatoes, such as desiree, peeled and cut into 4cm pieces (650g-700g net weight)
400g Swiss or rainbow chard, leaves and stalks separated, then roughly sliced
1 litre vegetable stock (or chicken or beef, if you prefer)
1½ tbsp coriander leaves, finely chopped
2 spring onions, finely sliced on an angle

Put the lentils in a medium saucepan, cover with plenty of cold, lightly salted water and bring to a boil.
Turn down the heat to medium and simmer for 20-25 minutes, until the lentils are nearly cooked but still retain a bite, then drain.

While the lentils are cooking, put 80ml oil in a large, heavy-based pot for which you have a lid, and put on a medium heat.
Once hot, add the onions, garlic, cumin, lemon skin, two and a quarter teaspoons of salt and plenty of pepper.
Cook for about 15 minutes, stirring often, until very soft and golden.
Stir in the potatoes, lentils and chard stalks, pour in the stock and 800ml water, bring to a gentle simmer, then cover and leave to cook for 20 minutes, or until the potato is soft but still holds its shape.

Turn off the heat, stir in the lemon juice and chard leaves, and leave to cook in the residual heat for two or three minutes, until wilted.
Divide between four bowls, drizzle over the remaining two tablespoons of oil, garnish with the coriander and spring onion, and serve hot.