I'm a UK citizen who really wants to travel to Iran this July/August (I haven't got Israeli stamps). I've read that I can apply for a visa directly through the Iranian embassy.
You can refer to the Iranian embassy in your country and ask for a visa to be issued for you. Usually this way takes longer time about 30 days so it is not suggested. By the way, some of the embassies ask for an invitation letter, in this case you have to use the below option.
Fill in the visa form on Iran visa application, it takes about 3-7 working days to get your reference number and two working days to collect your visa at the embassy by direct referral or one working week by posting the docs to the embassy. You can pay the visa fee in cash in Iran.
Check the cheapest Iran tours.