Heat the vegetable oil in a small saucepan over medium heat. Sprinkle in the cumin seeds, cooking briefly till they sizzle.
Add the onions and salt. Slowly cook, stirring frequently, until browned, 20 minutes or so. Reduce the heat to prevent burning.
Transfer to a small plate and reserve.
Pour the vegetable oil into a large saucepan over medium heat. Add the onion and cook until soft and translucent, 5 minutes or so.
Stir in the garlic, cumin, coriander, allspice, cinnamon, and ginger and cook briefly to release their full flavours, just 1 minute.
Add the lentils, water, and salt. Bring to a oil, reduce the heat to a slow simmer, cover tightly, and cook for 12 minutes.
Stir in the rice and raisins, cover, and continue cooking until the rice is tender and fluffy, 20 minutes or more.
Without uncovering, remove from the heat and let sit for 10 minutes.
Bring the water and salt to a full simmer in a large saucepan over medium heat.
Stir in the kale, cover tightly, and cook just until the leaves are bright green and tender, 3 minutes or so.
Drain well, then stir in the preserved lemon dressing (or another lemon-based dressing).
Form a bed of kale on individual plates or a large shared platter.
Spoon the mujadara on top, and top with cumin browned onions.