Parboil the rice. Bring a medium 2 quart saucepan of water (about 4 cups) to a boil. Add 1 teaspoon of kosher salt and add the lentils. Cover, reduce heat to low, and simmer for 12-15 minutes until the lentils are slightly tender but still hold their shape. Drain the lentils into a strainer over the sink and then transfer them to a small bowl to cool slightly.
Rinse the rice. Rinse the rice with cold water through a fine mesh strainer and set it aside to drain.
Caramelize the onions. Heat the same pot that you used for the lentils over medium heat. Add the olive oil, and once the oil is hot, add the onions and let them cook for 8-10 minutes, stirring occasionally, until they're starting to brown. Add the cumin, coriander, and turmeric and cook for another minute, until the spices are fragrant.
Cook the rice. Stir in the rice and cook for 1 minute, stirring often, to toast the rice. Add in the lentils, stock or water, bay leaf, and cinnamon stick and season everything with salt and pepper. Bring to a simmer, cover, reduce the heat as low as it can go and cook for 18 minutes. Remove the rice from the heat but leave it covered for an additional 10 minutes.
Fluff the rice with a fork and discard the cinnamon stick and bay leaf. Season to taste with salt and pepper, as needed.