Add the lentils, potato, ground coriander, and one of the crushed garlic cloves. Add water to just cover, and bring to a boil. Turn the heat down to medium and simmer until the lentils are nearly cooked.
Add the chard leaves and simmer a further 10 minutes.
Take off the heat and stir in the second garlic clove, the cilantro leaves, the lemon juice and salt to taste.