I created this on the fly one evening, and even my very picky son liked it well enough that he wants to have it again. You can save some time by cooking the lentils and couscous while the vegetables simmer. I serve it as a vegetarian main dish, but it could be a side dish just as easily. Za'tar is a mixture of thyme and sesame seeds, and sumac is a citrus-flavored spice that is made from crushed sumac berries--NOT to be confused with American poison sumac that is not edible. Both can be purchased in Mediterranean grocery stores or online.