(CNN) Salma Hayek was sitting in her car when she got the call. It was British Vogue editor Edward Enninful, a longtime friend of hers, asking if it was OK to patch in someone very special. Hayek was expecting their mutual friend Naomi Campbell to pop on the line.

"I was in the car and he said, 'Listen, I'm going to put somebody on the phone. Are you in the car with people?' I said 'Yes.' He told me 'you cannot say the name of the person I'm calling.' Frankly, I thought it was a joke. And we are also very good friends with Naomi Campbell. And I thought, they're pulling my leg or something, you know? I said, 'Oh, she's in London and he's gonna pass me to her," Hayek tells CNN. "But then it took a while for the other person to get on the phone. Then she got on the phone and introduced herself."

It was Duchess of Sussex Meghan Markle.

Hayek had never met her. Enninful didn't get on the phone again, leaving the two women to talk.

"She introduced herself and was very kind and loving and easy going," Hayek says, adding that Markle started to explain a future "project in support of women" she was working on.

Hayek says because she's worked with women's charities for 25 years, she was expecting Markle to inquire about teaming up for a specific organization she had in mind. (Hayek is on the board of the Kering Foundation, which combats violence against women, and helped with Chime for Change, a campaign for Gucci to promote women's rights worldwide. She is also an advocate for refugees.)

"I got excited. I'm thinking and I'm trying to find the logic to this strange day," Hayek recalls. "She explained her passion for women and what's happening currently. And then she said she's doing this with British Vogue. She said, you know, she was the guest editor of British Vogue, and I'm thinking maybe it's going to be an article on what we're doing, you know, with Kering and women, and she said no, 'I'm [doing a cover], I'm not going to be the cover, I'm putting my favorite women on the cover. And you're definitely one of them. You one of the first ones.' I was like completely shocked. I did not see it coming that way. She started talking about how she's been watching me and why me."

Their chat kicked off a months-long top-secret mission to get the cover shot and on stands by August with none of the other women involved knowing exactly what -- or who -- they were shooting for.

Gathering at a photo shoot in London, Hayek sat on what she knew; she was told she couldn't even tell her husband, daughter, or publicist. "I couldn't talk about it and I didn't," she says.

"I felt very honored when we did this photo shoot. No one else knew what it was for," she explains. "Only me and the photographer, Peter Lindbergh, knew. And all the girls were getting their picture taken for the cover and they didn't know that Meghan was how they got there."

Being able to talk about it now, Hayek adds, feels like freedom. She received a happy call from both Enninful and Markle earlier this week to congratulate her on pulling off the mission.

The theme of the next edition, scheduled to be released on August 8, is "Forces of Change." It will feature 15 women who have inspired Markle, who was originally offered to appear on the cover, according to the publication, but suggested a guest editor role instead.

She is the first guest editor of the September issue in the magazine's 103-year history.

"I loved that she didn't want to be on the cover," Hayek says. "She used her light to put it upon others, the ones who inspired her."

The Oscar-nominated actress and advocate says at one point she felt "embarrassed" to be chosen with the other featured women and didn't deserve the honor, but she's since come around to the idea with the hope the opportunity will allow her to bring even more awareness to women in need.

"The thing is that now there's so many amazing things happening," she says, "It was kind of interesting for me that she noticed me in this new wave of excitement about change. She really knew what she was talking about. I started on this path so long ago, and I did it quietly... A lot of the work I did was not about awareness, at the beginning I would go to the places, do the work. I started doing a lot of what people can't see, a lot of strategy."

Strategy like making sure in her longtime deal with Revlon, the cosmetic company started to include information about domestic violence and a hotline number for women in their pamphlets.

Beyond their Vogue collaboration, do Markle and Hayak have plans to meet?

"Maybe," she teases. "Maybe it's not something you're gonna see."

"I think we had a connection before we even talked to each other. The shock is that this person had been watching me and I had no idea. It's really beautiful and I really do think that we have a special connection."