Place the lentils in a saucepan and cover with water.
Bring to the boil, cover and let cook for about 20 minutes.
In a large casserole heat the oil and in this brown the onion.
Add the garlic and coriander, stir well and then add the spinach. Saute for 5 - 6 minutes, stirring frequently.
Add the potatoes, lentils and enough of the lentil cooking liquor to cover.
Season to taste with salt and pepper, bring to the boil, lower the flame and simmer until the mixture is thick and soupy (about 1 hour).
Stir in the lemon juice. Serve hot or lukewarm.
(Source: Daniel Rogov)