Asked by PEOPLE about her bond with the late actor Wednesday on the red carpet during the premiere of Sidney at The Academy Museum of Motion Pictures in Los Angeles, Winfrey, 68, said, "I don't know if I can even explain what it is because I had a bond with him that I really didn't or haven't had with anyone else."
"It's like being in relationship with someone where you feel fully, completely, most wholly seen. That's what it was," added Winfrey, who executive produced the upcoming Apple TV+ documentary about Poitier's life and legacy.
For Cher, 76, the music and acting legend said her favorite thing about Poitier was "that he was so easy to make blush."
And while they "didn't have a long history," Cher told PEOPLE, "I felt we had a nice history. When he came to some barbecues that I had, [his wife Joanna Shimkus] was all smiles and whatever, and he was game, he was going for it, but he was a little bit like that. But it was a tough crowd."
Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human-interest stories.
Eric Charbonneau/Shutterstock Cher and Oprah Winfrey at the premiere of Sidney
Poitier — a trailblazing actor/director and activist who, in 1964, became the first Black actor to win the Oscar for Best Actor — died in January, at age 94.
According to an official document obtained by PEOPLE later that month, Poitier died from cardiopulmonary failure. The document also listed that he had suffered from Alzheimer's dementia and prostate cancer over the years, and that he would be cremated.
Jon Kopaloff/Getty; Kurt Krieger/Corbis/Getty; Jon Kopaloff/Getty From left: Oprah Winfrey, Sidney Poitier, Cher
Beyond acting, Poitier was an advocate who fought for civil rights, often alongside his close friend of nearly 80 years, Harry Belafonte. They helped organize the March on Washington and plan Martin Luther King Jr.'s memorial after his assassination.
RELATED VIDEO: Sidney Poitier, First Black Man to Win Best Actor Oscar and a Titan of Cinema, Dead at 94
Shortly after Poitier's death, Deadline reported that Apple Original Films was producing a feature about him, with Winfrey signed on as an executive producer through Harpo Productions and Network Entertainment.
According to the outlet, the media mogul and Apple teamed up for documentary over a year ago. Poitier's family also participated in the project, with Reginald Hudlin directing.
In a statement to Variety after his death, Poitier's family said, "To us Sidney Poitier was not only a brilliant actor, activist and a man of incredible grace and moral fortitude, he was also a devoted and loving husband, a supportive and adoring father and a man who always put family first."
"He is our guiding light who lit up our lives with infinite love and wonder," they added.
Sidney premieres Friday on Apple TV+.