Begin by rinsing the brown lentils and placing them in a medium-sized pot. Cover with water, bring to a boil, then reduce the heat to a simmer. Cook until the lentils are tender but still hold their shape, about 20-25 minutes. Drain and set aside.
In a separate pot, cook the rice according to package instructions until it's fluffy and fully cooked. Set aside.
Meanwhile, cook the elbow macaroni in a pot of boiling salted water until al dente. Drain and rinse under cold water to stop the cooking process. Set aside.
In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add the thinly sliced onions and cook, stirring occasionally, until they are caramelized and golden brown, about 15 minutes. Remove half of the onions for garnish and set aside.
To the skillet with the remaining onions, add the cooked lentils, rice, and macaroni. Season with salt and pepper, then mix well. Keep warm.
For the cumin-scented tomato sauce, heat 1 tablespoon of olive oil in a saucepan over medium heat. Add the minced garlic and ground cumin, cooking until fragrant, about 1 minute.
Add the crushed tomatoes, white vinegar, and sugar to the saucepan. Season with salt and pepper. Bring to a simmer and cook for 10 minutes, allowing the flavors to meld.
To serve, plate the Koshari mixture and pour the cumin-scented tomato sauce over the top. Garnish with the reserved caramelized onions and chickpeas. Sprinkle crispy fried onions for an added crunch.