Rinse the lentils well in several changes of water until it runs clear. Put the lentils and all the ingredients except the lemon juice and coriander in a medium saucepan. Add 400ml water to the pan then bring to the boil.
Turn down and simmer gently, stirring occasionally, for 30-35 minutes, until the lentils are soft. Season with the lemon juice and more salt, if needed. Serve with steamed basmati rice, if liked, and scatter with the coriander leaves.