They say a boy’s best friend is his mother. For director Nathan Silver, she’s also his muse.

Over the last decade, teacher Cindy Silver has appeared in several of her son’s films, as well as his 2019 docuseries, “Cutting My Mother.” Their latest collaboration, “Between the Temples” (in theaters now), is a wry and tender riff on “Harold and Maude” that follows a widowed cantor named Ben (Jason Schwartzman) and his much older pupil, Carla (Carol Kane), as she studies for a late-in-life bat mitzvah.

The comedy is loosely inspired by Cindy’s experience as a culturally Jewish woman, who at 68, enrolled at her local temple in Kingston, New York, in a b’nai mitzvah class (a gender-neutral term for multiple people going through the ritual). She doesn’t star in the movie, although she makes a cameo.

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“This role needed a real actress, not just his mother,” jokes Cindy, 74, on a late-morning Zoom call with Nathan, 41, who lives in Brooklyn. She is “thrilled” and “happy” to help promote the film, but “I’m also just excited to look at my son! We don’t get to see each other too much.”

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How Cindy Silver's bat mitzvah journey helped inspire the movie 'Between the Temples'

In Judaism, bar and bat mitzvahs are widely considered a teenage rite of passage, signaling a grown-up step forward into the religious community. As such, “Between the Temples” offers a rare onscreen depiction of the ritual for adults, joining a unique pop-culture pantheon that includes episodes of “The Simpsons,” “Touched by an Angel” and “The Dick Van Dyke Show.”

“That’s Mount Rushmore!” Nathan says with a laugh. “I’m honored.”

There are a variety of reasons why someone may not have a mitzvah when they’re young: the financial pressures of a blow-out party; the relative rarity of bat mitzvahs until the 1970s; or the months-long preparation required, which can prove challenging for children with different learning abilities. Some kids feel that a bar or bat mitzvah doesn’t align with their gender expression, while others may not convert to Judaism until they’re well into adulthood. Older members of the community might have been prevented from having a ceremony during times of Jewish oppression, such as the Holocaust.

Cindy grew up in Queens, New York, in a secular Jewish home. “My mother would make veal parmesan, and my friends who had kosher households would come to eat at our house,” she recalls. Instead of going to temple, “we’d go to Pete Seeger concerts. But my dad was always saying Yiddishisms, which drove my mother crazy, and she could not stand that I had a sing-song Jewish inflection, which I got from my father.”

Although her parents weren’t religious, they taught her the values of Judaism from an early age: “My dad was always banging the table, screaming, ‘If you have your health, you have everything! Just do good in the world!’ That’s a very Jewish ideal: tikkun olam, ‘repairing the world.’ ”

Like his mom, Nathan wasn’t raised religious and didn’t have a bar mitzvah. Growing up, “my whole Jewish DNA was the humor,” says the filmmaker, who had an early appetite for “Seinfeld” and Mel Brooks comedies. But he’s always been fascinated by how people connect spiritually and to each other.

“What interests me about Judaism is it's a religion of questions. Every question is met with another question,” Nathan says. Rather than worry about the afterlife, Judaism implores people to focus on the now and “embrace what’s in front of you. And I think that’s essential for the characters in this movie: They need other people in order to find themselves.”

In the film, an unlikely love story blossoms between Carla and Ben as they prepare for her bat mitzvah. That aspect of the movie is not true to life. (Cindy's husband of 55 years, Harvey, is just off camera as she chats.) But she could relate to the community that Carla finds in going to temple.

Six years ago, after a friend’s partner died, “we all decided to rally around her and have a b’nai mitzvah together,” Cindy says. Initially, she was “entranced” by her dive into the Jewish faith: “I was going to the rabbi’s studio for meditation and Torah study, and it was brilliant. It’s all discussion and coming up with what everything means, and I love that about Judaism. I felt very accepted because my rabbi would take anyone in. I was like, ‘I want to learn more.’ “

The movie resonates with adults who chose late-in-life bar mitzvahs and bat mitzvahs

But eventually, Cindy and her friends dropped out of the class, discouraged by some of the required reading and memorization. Carla faces similar ups and downs in "Between the Temples," which is part of why the movie has resonated with viewers since its Sundance Film Festival debut in January. Nathan says he’s met many older filmgoers on their own religious paths, some of whom have recently had bar or bat mitzvahs: “It’s neat to have them say that it really reflected their experience.”

One of those audience members was Rivanna Hyman, 74, a Long Island resident. She technically became a bat mitzvah around age 12 while visiting family in Israel, more on a whim and without the same prep and prayer responsibility. But for decades, “I felt I had not earned the bat mitzvah title that was bestowed upon me,” Hyman says. So at age 48, after two years of study, she and 10 other women had a b’not mitzvah (the plural for women and girls).

“I could understand Carla's desire to achieve this milestone in her life,” Hyman says. “For all audiences, I hope they will come away with a greater understanding of the need for someone to accomplish a specific goal."

As for Nathan's mom, she's not interested in resuming her studies for a bat mitzvah. Rather, "I would like to keep reading and exploring on my own,” Cindy says. “I’ll continue my journey as a Jew, but not in a temple because I’ve moved on. And my husband was dragged to services after 50 years – he does not want to go to them!"