Heat the vegetable oil in a large skillet over medium-high heat. Add the sliced onions and fry for 12 to 15 minutes, stirring frequently, until they are deeply caramelized, crispy, and dark golden brown. Remove the onions with a slotted spoon to drain on paper towels, reserving the flavorful onion-infused oil left in the skillet.

In a medium saucepan, bring 2 cups of water to a boil. Add the brown lentils, reduce heat to low, cover, and simmer for 15 minutes. Stir in the rinsed white rice, 1 teaspoon of cumin, salt, 2 tablespoons of the reserved onion oil, and 1.5 cups of additional water, then cover and cook for another 15 minutes until both the rice and lentils are tender.

While the grains cook, bring a large pot of salted water to a boil. Cook the elbow macaroni according to the package instructions until al dente, which takes about 8 minutes. Drain the pasta and immediately toss it with 1 tablespoon of the reserved onion oil to prevent sticking.

To make the tomato sauce, heat 2 tablespoons of the reserved onion oil in a small saucepan over medium heat. Add the minced garlic and cook for 1 minute until fragrant and lightly golden. Stir in the tomato paste, tomato sauce, white vinegar, coriander, remaining cumin, salt, and black pepper, then let the mixture simmer on low for 10 minutes until slightly thickened.

In a small pot, combine the drained chickpeas with 2 tablespoons of water and a pinch of cumin. Cover and heat over low for 5 minutes until warmed through.

Assemble the dish by layering the warm spiced lentil and rice mixture at the bottom of a large serving bowl. Add a layer of elbow macaroni on top of the grains, then generously ladle the warm garlic-tomato sauce over the pasta. Garnish with the warmed chickpeas and a mountain of the crispy fried onions before serving warm.