Rinse and pick over the Brown Lentils and rinse the Long-Grain White Rice until the water runs clear; drain and set aside.
Thinly slice the Onions. Heat a generous drizzle of Olive Oil in a large skillet over medium heat and cook the onions slowly, stirring occasionally, until they turn deep golden brown and crisp at the edges (20–30 minutes). Remove about half the onions to a bowl to use as a topping and keep the rest in the pan.
In a medium pot, combine the drained lentils with enough Water to cover by about 1 inch. Bring to a simmer and cook until the lentils are just tender (about 15–20 minutes), then season with Salt, Ground Cumin and a pinch of Black Pepper.
Add the drained rice to the pot with the lentils, stir gently, and add more hot water if needed (the water level should be about 1/2 inch above the rice and lentils). Bring back to a simmer, cover tightly, reduce heat to low and cook until the rice is tender and liquid is absorbed (about 15 minutes).
Remove the pot from heat and let it sit, covered, for 5–10 minutes. Then fluff the rice and lentils gently with a fork.
Fold most of the reserved caramelized onions into the lentil-and-rice mixture for flavor and texture, reserving some for garnish. Taste and adjust seasoning with additional Salt and Black Pepper if needed.
Whisk together the Plain Yogurt with the juice of the Lemon and chopped Fresh Parsley; season this sauce to taste with a little salt and pepper — it should be bright and tangy to cut through the richness of the dish.
Serve the mujadara warm, topped with the remaining caramelized onions and a drizzle of Olive Oil if you like. Offer the lemony yogurt on the side or spooned over the top, and garnish with extra Fresh Parsley for color.
