Place the lentils in a saucepan with 7 cups of water and bring to the boil.
Cover and simmer until tender.
Brown the onions in oil.
Add the chopped spinach and the garlic crushed with salt, and mix well.
Saute slowly until the spinach becomes soft.
Bring the lentils back to the boil and add the celery and the sauteed mixture.
Turn the heat to low and sim- mer slowly for 5 minutes.
For a thin soup, mix in the lemon juice and adjust salt to taste.
For a thicker soup, mix the cornflour/corn- starch with the lemon juice before adding it to the cooked soup, then allow soup to simmer for a few min- utes longer.