Taken from the Sunday Times 14th Jan 2018
Heat the olive oil in a large pan and set over low heat. Add the onion and celery with a pinch of salt and cook covered with lid on for 15 minutes, until they are soft but without colour.
Add garlic and turmeric and cook for another few minutes. Now add lentils and stir to coat them in the onion mixture. Add the stock and simmer over medium heat for 15-20 mins until they are soft and tender. While warm, season the lentils with salt, black pepper and lemon juice.
Add the spinach and blitz to a rough texture. Ladle the soup into shallow bowls and finish with the olive oil and a spoonful of yogurt.