Onion cut into thin slices, as done here, is called busal mrayyash (feathered onion) in Iraqi culinary terminology. It is a simple relish and yet so delicious with all kinds of grilled meat.
Method
Cut a medium onion in half lengthwise, then slice it thinly crosswise (as thin as possible).
Put the slices in a small bowl, add 1teaspoonvinegar