“It’s the craziest thing I’ve ever seen in my life,” said Benny Blanco, who co-produced the hit track

Sia in November 2023; Rihanna in April 2024. PHOTO: MICHAEL LOCCISANO/WIREIMAGE; STEVE GRANITZ/FILMMAGIC

• Benny Blanco told Howard Stern that watching Sia work is “the craziest thing”
• The producer revealed that she wrote “Diamonds” in five minutes while waiting for a cab she’d ordered to arrive
• The song ultimately went to Rihanna and became a massive hit

Sia is one of the speediest songwriters in the game!

The hitmaker, 48, penned one of her most well-known tracks, Rihanna’s “Diamonds,” in the time it took to call for and wait for a cab, per Benny Blanco.

While appearing on SiriusXM’s The Howard Stern Show on May 14, Blanco (who witnessed the moment and co-produced the 2012 hit with producing duo Stargate) recalled the slim window in which Sia wrote it — and, apparently, her other songs as well.

“Sia writes a song in under five minutes,” the producer, 36, told host Stern. “It’s the craziest thing I’ve ever seen in my entire life.

“She was waiting for a cab — this was before Uber — and they said it’s going to be 15 minutes,” he recalled. “And she said, ‘Oh, well just load up another thing.’”

And that’s all it took to pen the iconic track. “Song, melody, lyrics, harmonies, everything all done before the cab comes,” said Blanco. “And she’s like, ‘Yeah, that’s pretty good.’ ”

Had Sia’s taxi come earlier, the world may have never heard “Diamonds,” which became Rihanna’s 12th No. 1 hits on the Billboard Hot 100, and spent three weeks there, per Billboard.

And, after Stern wondered why Sia — who has done vocals for hit tracks like “Chandelier” and “Cheap Thrills” — would give a hit like “Diamonds” to another artist “like it’s a throwaway,” the producer defended the decision.

“You have to remember, a lot of people are songwriters,” Blanco told the host, adding that “you never know how a song’s going to feel or how it’s going to hit you.”

Added Blanco: “Rihanna is such a special artist that the second her voice touches something it’s like a firework. She has so much tone and personality.”

Benny Blanco visits SiriusXM’s ‘The Howard Stern Show’ in Los Angeles on May 14, 2024. EMMA MCINTYRE/GETTY

Selena Gomez and Benny Blanco’s Relationship Timeline

The producer and cookbook author also recalled the moment he first felt those fireworks himself, telling Stern, “When we first made the demo I was like, ‘This is cool. I don’t know.’ ‘Cause we wanted to give the song, at the time, to Kanye or Eminem.”

“And actually, Eminem recorded a song to it but he didn’t say anything ’til like a year late later until it was about to come out. It was crazy. And I just remember in that moment being like, ‘Oh this is cool.’”

“But then once Rihanna sang it, I was like, ‘Oh my God, this is something,’” he added.

Benny Blanco with Sia and her husband Dan Bernad in Los Angeles in June 2023. CHELSEA LAUREN/SHUTTERSTOCK

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.

Blanco, who has produced songs for artists including Ed Sheeran, Katy Perry and Selena Gomez, whom he is currently dating.

Elsewhere in his conversation with Stern, he said he sees marriage in he and the pop star’s future, adding, “I gotta get my act together.”

Also booked and busy, Sia is currently executive producing an album for Paris Hilton. Speaking with Billboard last month, the “Stars Are Blind” singer opened up about the collaborative project.

“No one really knows this, but I’m actually a very shy person, like painfully shy,” said Hilton. “But with [Sia], I just feel so comfortable so I really sang in ways that I never knew were possible.”