Wa `alaykum As-Salamu waRahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Answering your question, Dr Khaled Hanafi, Head of the Fatwa Committee in Germany and member of the ECFR, states:
Most attendants of these gatherings do not belong to the groups authorized to receive Zakah such as the poor and the needy. Rather, they are well-to-do people who want to enjoy the company of their fellow Muslims, to relish Ramadan atmosphere and to attend Isha ad Tarawih prayers.
However, the importance and significant reward of this Ramadan activity is emphasized. The Prophet (peace and blessings be upon him) said: “Whoever gives food for a fasting person to break his fast, he will have a reward like theirs, without diminishing in any way the reward of the latter.” (At-Tirmidhi)
So, these iftars can be funded through charity (sadaqah), not Zakah.
Almighty Allah knows best.