I mean, what could be more obvious?
[/sarcasm]
I'm looking forward to hearing a legitimate description of the symbol. Good thread, good question.
Cuhail

In the middle of the Iranian flag, is a centre piece which has been arranged to symbolise the Arabic script for ‘Allah’. The script is formed of four crescents (the crescent is a central Islamic symbol) and a sword. Above the sword is the Arabic ‘shaddah’ symbol which is placed above particular letters in the Arabic script to strengthen the respective sound. In the case of the Iranian flag, the shaddah ‘strengthens’ the sword. The representation of ‘Allah’ in the Arabic script is also formed in such a way that it symbolises a tulip. The use of the tulip in Iran dates back to ancient time, whereby it has been used to represent the death of individuals who have died for their country. It has been placed in the Iranian flag to honour the Iranians who died fighting in the Iraq-Iran war.
The Khanda constitutes three symbols in one. However, the name is derived from the central symbol, Khanda, a special type of double-edged sword which confirms the Sikhs' belief in One God. * The double-edged sword is the creative power of God which controls the destiny of the whole creation. It is sovereign power over life and death. * The right edge of the double-edged sword symbolizes freedom and authority governed by moral and spiritual values. * The left edge of the double-edged sword symbolizes divine justice which chastises and punishes the wicked oppressors. * On the left side is the sword of spiritual sovereignty, Piri; on the right side is the sword of political sovereignty, Miri. There must always be a balance between the two and this balance is emphasized by a inside circle. The circle is what is called the Chakra. This is a symbol of all-embracing divine manifestation including everything and wanting nothing, without beginning or end, neither first or last, timeless, and absolute. It is the symbol of oneness, unity, justice, humanity and morality. The Chakra was also used by the Sikhs as one of the war weapons against injustice and oppression. Almost all Sikh warriors used to wear it in the eighteenth century.
What, it's OBVIOUSLY an onion. The Iranians are known worldwide for their unhealthy love of onions. I mean, what could be more obvious?