In a medium saucepan, cook lamb over medium heat. As it browns, season with salt and pepper and a sprinkle with some cumin. When fully cooked, remove lamb from pan and set aside. To save dishes, use the same saucepan to cook the spices and onions.
Add lentils to a medium saucepan. Fill with enough chicken broth to cover the lentils by about an inch. Bring it to a boil over medium-high heat, then turn down to a simmer and cook until the lentils are tender, but not mushy, and the liquid is fully absorbed, about 15-20 minutes.
While the lentils cook, heat oil in a large skillet.
When the oil easily swirls around the pan, add the cumin seeds and pepper. Toast the spices, shaking the pan every once in a while, until the cumin seeds darken a touch, about 1 minute.
Add the onions, sprinkle with a dash of salt and cook until they turn dark caramel brown, stirring often. This will take about 20-30 minutes. Splash the onions with a little water if they stick to the bottom of the pan.
The onions are done when they turn a deep caramel brown color and the onions around the edges of the pan will start to get a bit crispy.
Using a slotted spoon or spatula, remove about half of the onions to a paper towel-lined plate.
Sprinkle in the ground cumin, cayenne and then add the cinnamon stick; saute about 1 minute.
Add the rice and cook, stirring often to toast the rice a bit. After 1-2 minutes, add the cooked lentils (you can also serve them on the side if you have non-lentil eating people in your family), 3 cups of water and 1 1/2 teaspoons of salt; bring to a boil.
Turn the heat down to low so that the pan is at a low simmer, cover and cook 30 minutes.
You'll know it's done when the water is completely evaporated, and the rice should be cooked. Depending on your stove, you may need to add or subtract 5 minutes.
When the water is absorbed and the rice is cooked turn off the heat, keep the lid on, and allow the rice to steam undisturbed for about 5 minutes. This makes the rice extra fluffy, so don't skip this step. You can use this 5 minutes to pour yourself a glass of wine, you've earned it!
Taste the rice for seasoning.
Stir in the lamb until the lamb is combined with the rest of the ingredients.
Serve with the reserved caramelized onions, toasted pine nuts, if using, and a little squeeze of lemon juice.
I also like to serve this with some Greek yogurt. I mix in some chopped cilantro and a squeeze of lime juice to the yogurt to add more flavor to it.