Rinse lentils. Place in a large pot with 7 cups of water and bring to a boil. Reduce heat, cover and simmer for 15 minutes.
While the lentils are simmering, halve, peel, and slice the onions.
Add the rice to the lentils. Return to a boil, reduce heat, cover and simmer for and additional 15 minutes. Remove pan from heat and let sit for 10 minutes before removing the lid.
While the lentils and rice are simmering, add the onions and olive oil to a large skillet. Cover and cook 15-20 minutes or until golden brown and caramelized. (Stir the onions every few minutes to avoid burning. If the bottom of the pan begins to brown, add 1 tablespoon of water.)
Add the cumin, cinnamon, salt, pepper, and half of the onions to the lentil and rice mixture and gently combine. Plate up your servings and then top with the remaining onions.
Notes
I use brown lentils in my mujadara, but you could substitute green lentils. Just don't use the red lentils, as they might turn to mush.
I use jasmine rice in my mujadara, but you could substitute basmati. If you choose to use another type of rice, you may need to adjust the cooking time.