If the couscous is instant, follow the instructions on the packet.
For non-instant couscous, place the couscous into a large bowl. Fill a stock pot or large pasta pot 3/4 of the way with water. Bring water to a boil. Pour the couscous into the boiling water and stir. Cook for 7 to 8 minutes until the couscous is tender. Drain the couscous and toss in preserved lemon and cilantro. Season with salt and pepper.
Quick preserved lemon: Slice 2 lemons into 1/4-inch slices, lay out on a plate and salt on 1 side. Turn over and salt the other. Stack on top of themselves and let sit for 20 minutes in a baking dish. Rinse gently with cold water and dice into 1/2-inch pieces.