Iran is a multi-ethnic country.: Every country is associated with a major ethnicity. Germans with Germany. French with France. Swedes with Sweden.
An American is a European American.
A Pakistani is a Sindi or Punjabi. A Pashtoon from Pakistan says I am a "Pashtoon from Pakistan". He does not say that "He is a Pakistani".
An Afghan is also a Bactrian whether Pashtoon or Dari speaking Bactrian. Dari speaking turks say they are tajiks from Afghanistan.
Also Russia has many ethnic groups. Those ethnic groups do not call themselves either as Russians. An Azeri or Uzbek citizen of Russia says he is an Azeri or Uzbek from Russia. They do not say "I am Russian".
A Kurd from Iran always says he is a Kurd from Iran. He does not say he is an "Iranian". An Iranian is related to the major ethnic group in Iran. Similar to all other countries. Iran has %40 Azeri Turks and %35 Persians as a proportion Iran's population. Azeri Turks are the major ethnic group in Iran.
Iranian is the name of Nationality. Iranian is not a race. Azeri Turks are "The Iranians". The other minorities identify themselves with their ethnic affiliation.
An Iranian is an Azeri Turk. Iranians are Turks. The rest of Iran identify their ethnicity and say that "I am Persian or Balooch or Lur etc from Iran".