Take olive oil in a large frying pan and fry the onions on medium heat until golden brown from all sides. Take out 2/3 of the onions and put aside for garnishing. Leave the rest in the pan along with the oil.
Take a large cooking pot, add the pre-soaked lentils and just enough boiling water to cover them. Cover and allow to cook on medium until al-dente.
Add rice, cumin and salt to the lentils. Mix and add the caramalized onions from the pan along with the oil.
Cover the rice and lentils with boiling water.
Bring to a boil, cover and reduce the heat to medium and allow to cook for 15 min. or until the rice has absorbed all the liquid. Add cinnamon, if desired.
Turn off the heat and wait for another 10 min. Don´t open the lid at this stage!
Transfer Mujaddarah in to a serving platter and place the reserved fried onions on top.