Lemon is the perfect accent for lentils and Swiss chard - the main ingredients in this meal-in-a bowl soup from Lebanon. Enjoy it as an entree accompanied by black bread and cucumbers with yoghurt.
Rinse lentils; sort through and discard any foreign material. Drain well. Combine lentils and stock in an 8-quart pan; cover and bring to simmering.
Peel potato and cut into 1/2-inch cubes; add to lentils. Cover and simmer for 20 minutes. Slice chard leaves and stems crosswise in 1/2-inch wide strips. Add to soup, cover, and continue simmering until lentils are tender (about 20 more minutes).
In a small frying pan over medium heat, cook onion in oil, stirring occasionally, until onion is soft and golden (about 10 minutes). Add to onion 1/3 cup of the fresh coriander along with garlic and cook for 1 to 2 minutes.
Add onion mixture to soup during the last 5 minutes of cooking. Stir in salt to taste, pepper, cumin, and lemon juice. Garnish soup with lemon slices and top with the remaining chopped coriander.