Mr Nisman, a non-practising Jew, had accused President Cristina Fernández de Kirchner and her Jewish foreign minister, Héctor Timerman, of conspiring to shield former Iranian officials he suspected of masterminding the 1994 attack, in return for trade benefits.
Mr Nisman was found dead in mid-January in his bathroom, hours before he was due to present his findings before Argentina's Congress. The pistol that fired the fatal bullet was beneath his body and a spent cartridge was also at the scene.
The investigation into his death is ongoing. Forensic experts are veering toward suicide, but a separate investigative team put together by Mr Nisman's former partner says he was murdered. Mrs Kirchner has suggested he was fed misleading evidence and then killed in an elaborate plot to destabalise her government.
Mr Nisman's accusations of a political cover-up were finally dismissed in May after prosecutors and judges had said they were completely unfounded. But many Argentines, like Ms Guterman, believe Mr Nisman's evidence warranted further investigation.
At Friday's ceremony, which was planned to take place a day before the anniversary of the bombing, July 18, because of Shabbat, the names of the 85 victims were to be read and a siren sounded at 9.53am, which was the precise moment of the explosion 21 years ago.
A team of four prosecutors was appointed to replace Mr Nisman. The Amia investigative office has been one of the largest and best funded prosecutor's offices in the country. But there are so many tangents within the investigation that few people believe it will progress.
Aside from the mystery of Mr Nisman's death, a court has still not decided on the constitutionality of a 2013 agreement between the governments of Iran and Argentina to try to expedite the investigation, which Mr Nisman had claimed was a cover-up of a secret pact between the two governments.
Added to this, after years of delay, a trial in which former officials are accused of a separate cover-up begins next month.
"We're never steering events; we're always reacting to them," said Waldo Wolff, a former prominent Jewish community leader who delivered a speech at Mr Nisman's funeral. "As time goes on, not only is there no justice, but there are more and more problems."
Luis Czyzewski, now in his 70s and a former auditor at Amia, lost his 21-year-old daughter in the attack.
In an interview, he recalled running toward the headquarters past shards of glass and broken blocks of masonry after he heard about the bombing on the news. He fought past police officers, who had sealed off the bomb site, and found his wife alive, her face blackened with dust.
Their daughter, Paola, who had taken the lift down to the entrance to collect a take-away coffee, was one of the first people to die in the blast, experts later told Mr Czyzewski.
"With each passing day, I'm less convinced that [the bombing will be solved]," he said.
