Onion is a vegetable which is almost like a staple in Indian food. This is also known to be one of the essential ingredients of raw salads. They come in different colours like white, red or yellow and are quite in demand in cold salads and hot soups. You can dice, slice or cut it in rings and put it in burgers and sandwiches. Onions emit a sharp flavour and fragrance once they are fried; it is due to the sulphur compound in the vegetable.Onions are known to be rich in biotin.  Most of the flavonoids which are known as anti-oxidants are concentrated more in the outer layers, so when you peel off the layers, you should remove as little as possible.