Tambutti, born two years before the coup, knew her grandfather only through posters.
Forced to flee the country with her parents, she grew up in Mexico.
"My family dedicated itself to exposing Chile's human rights violations and to upholding my grandfather's legacy," she says.
"Paradoxically, within the family, we never spoke about him."
In 2007, she returned to Chile with a deep need to learn more about the man behind the public persona.
Unearthing intimate details from family members is not easy, particularly in the case of Allende's widow, Tambutti's 94-year-old grandmother.
"Tencha" is reluctant to talk, but with gentle and compassionate encouragement, she begins to open up about life with her husband.
Other members of the family are similarly unwilling to engage, and Marcia Tambutti begins to realise that her family's experience mirrors that of the entire nation.
Seeing their discomfort and pain, she begins to understand the complex emotions and politics that have ruled over them for over 40 years.
"My grandfather was one of the most controversial figures in my country, being either hated or truly loved and admired.
"As a consequence of the social turmoil that the coup created, Chilean society was wholly unable to deal with its political and social ruptures."
To break through this polarisation and the collective desire to forget a traumatic past, Tambutti seeks to recover the everyday man that was Allende, the one warmly nicknamed "Chicho" by his family, not the saint or the demon.
With great subtlety, she invites her family and the nation to reflect on, miss and mourn the man behind the stereotype, finally face the past, and consider how they might move forward.
"This personal angle on a famous historical event is the film's greatest strength," says Deborah Young of The Hollywood Reporter.
"One can understand how difficult it is to open old wounds, but most viewers will agree the director is right to insist on coaxing out the family truth before it is too late to put the tale together."
One applauds Chile's willingness to do the same, with the release of this film.
Beyond My Grandfather, Allende (Allende, mi abuelo Allende) screens at the Davis Lecture Theatre, Watt St, on Saturday, October 27 at 4pm. Entry is free, koha appreciated. Moviegoers are invited to a Fiesta of Hispanic food, music and dance after the screening.
