Lentil soup

Chop an onion, some carrot and celery and cook it slightly in a medium sized pot with some olive oil. Add abundant water and the lentils. Add a little salt, maybe some grated ginger if you like. Cover the pot and let simmer till cooked (30'). Serve with a squirt of fresh olive oil over the top.
A variant could be to add a diced potato when you add the lentils, this thickens the soup. You can also sprinkle some parmesan cheese when serving.
Here's an interesting variant: add some fresh orange juice to the soup when it's almost finished cooking.