Bring lentils and water to the boil in a covered pot
Reduce the heat and simmer for 20 minutes (don't salt them yet - it'll keep them hard)
Fry the onions in oil in a large pan over a low heat for about 20 minutes.
Remove half to add to the lentils.
Turn up the heat to medium/high and fry the remaining onions until almost caramelised.
Use as garnish
Add the rice and half the onions to the lentils.
Cook, covered, for another 20 minutes
Service on a large dish garnished with the caramelised onion