This puréed Middle Eastern soup is incredibly simple to make. The red lentils are flavoured with a single ingredient - cumin - which is very pleasantly refreshing.
Rinse the lentils and leave to drain. Heat the oil and butter in a large, heavy pan and stir in the cumin seeds. Cook, stirring, until they emit a nutty aroma. Add the onion, and when it begins to turn golden brown, stir in the lentils.
Pour the stock into the pan and bring to the boil. Reduce the heat, cover the pan and simmer for about 30 minutes, topping up wit