Drain the soaked lentils and pick out any debris.
Put the lentils in a medium pot and cover them with water that reaches at least an inch above the lentils. Boil the lentils for 15 minutes, until the lentils are three-quarters ready — they should be getting softer, but still al dente — drain them, and set aside.
While the lentils are boiling in another pot, heat the olive oil in a wide pan over high heat and fry the onions for about 10 minutes, until they are golden brown. You want to stir occasionally, so as not to burn them, but let them settle a bit so that they can brown nicely. Remove about one-third of the onions and set them aside.
Add the rice, salt, cumin, and turmeric to the remaining onions and mix them together. Fry the mixture for 1 to 2 minutes, until you can smell the spices, constantly stirring to prevent sticking.
Add the par-cooked lentils and vegetable broth. Boil the mixture for 10 to 20 minutes, until the cooked rice is tender.
When it’s ready, give everything a nice stir and place the reserved crispy onion on top.