The pecan (Carya illinoinensis) is the smooth, oval, reddish-brown nut of a giant North American hickory tree — the only major tree nut native to North America. Crack the glossy shell and out comes a deeply grooved, two-lobed kernel that is the sweetest and softest of the common nuts: buttery, rich and richly nutty with a gentle woody edge and almost none of the astringent bitterness that marks its cousin the walnut. Eaten raw or toasted, it is the soul of pecan pie, praline and butter-pecan ice cream, and toasting deepens it into something warm, caramel-edged and unmistakably roasty.