كتشبيه الجائع وجها كالبدر في الإشراق والاستدارة بالرغيف
As when a hungry person compares a round, shining face with a loaf instead of the moon.
The face and loaf can be compared in roundness and perhaps a bright or smooth surface, so the likeness is not meaningless. Yet choosing bread over the familiar moon image discloses the person's intense desire for food.
The rhetorical question is not whether bread is objectively more beautiful than the moon, but why bread comes immediately to this speaker's mind. The explanation lies in a psychological state and urgent concern. Merely listing the shared visual features would miss the special point of the simile.