"Diana was smiling from ear to ear all night," an insider tells PEOPLE. "You could tell she thought it was a great birthday celebration"

By Jordan Runtagh
March 27, 2019 03:05 PM

Diana Ross celebrated her birthday in a manner befitting her status as the Queen of Motown.

The iconic Supremes frontman turned 75 with a two-part celebration in Los Angeles on Tuesday night. The festivities began with a pre-party at the famed Hollywood hotspot Warwick on Sunset Boulevard, where Beyoncé serenaded her with an impromptu version of “Happy Birthday.”

Members of Diana’s large family (daughter Tracee Ellis Ross, son Evan Ross, and daughter-in-law Ashlee Simpson, among others) as well as longtime friends like Motown founder Berry Gordy and a multitude of stars — including Sean “Diddy” Combs, Robin Thicke, DJ Khaled, Heidi Klum, Chris Rock, French Montana, Kris Jenner, Kourtney Kardashian and Khloé Kardashian — all gathered around what Tracee dubbed “the biggest cake ever” to sing Diana “Happy Birthday.”

But when the 46-year-old Blackish actress saw Beyoncé in the crowd she quickly called the “Single Ladies” songstress over to take the lead instead.

Credit: 42/BACKGRID
Tracee Ellis-Ross.
| Credit: SPW/SplashNews.com
Khloe Kardashian and Kris Jenner.
| Credit: Hollywood To You/ BACKGRID
Koutney Kardashian.
| Credit: Bauer-Griffin/SplashNews.com

Bey, of course, delivered a “***flawless” version of the tune. Her hair pulled back in a long braided ponytail and wearing a black gown, she commanded the room. Everyone stayed silent as she sang the melody to a beaming Diana.

The emotional moment was captured by the cell phone cameras of onlookers like Khloé, who shared the moment to her Instagram story. The Hollywood Palladium’s Instagram account also shared video of the scene, which ended with Beyoncé and Diana embracing in a loving hug.

An insider tells PEOPLE that at 11 p.m. the party moved down the street to the Hollywood Palladium for an epic concert performed for — and by — the birthday girl, who made five different wardrobe changes as the night wore on.

Chris Rock.
| Credit: Bauer-Griffin/SplashNews.com
Heidi Klum.
| Credit: Bauer-Griffin/SplashNews.com

The live band ensured she had suitable entrance music by playing “I’m Coming Out,” her 1980 disco classic. Diddy kicked it off by rapping his own hit “Mo Money, Mo Problems,” which samples Diana’s tune, before the lady herself belted out the original lyrics.

According to Instagram stories from DJ Cassidy, Diddy’s three daughters — Jessie, 12, D’Lila, 12, and Chance, 13 — danced alongside Diana for a performance of “Stop in the Name of Love.” Diana joined in the grooving, even tearing off the train of her vintage dress so she could bust a move!

Other songs performed by Diana included “Come See About Me,” “The Boss” and “Your Love.”

Stevie Wonder made a special appearance at the midpoint of the evening, singing his own rendition of “Happy Birthday” to Diana. Not to be outdone, Leonardo DiCaprio (who brought his mom!) appeared onstage to wish Diana well. “Happy birthday to the legend, Diana Ross,” he exclaimed, according to E! News.

Robin Thicke teamed with Diana for a stirring version of the sweeping ballad “Endless Love,” while Ross’ son Evan and daughter-in-law Ashlee Simpson dueted on “Love Hangover.”

Evan Ross and Ashlee Simpson.
| Credit: SPW/SplashNews.com

Before the party was over, Diana invited the Kardashians in attendance onto the stage for a dance party to “Take Me Higher” from 1995.

“Khloe, Kourtney and Kris seemed to have a blast — they danced nonstop,” the insider says. As Diana tackled “Ease on Down the Road” next, she welcomed Evan and Tracee to the stage, too.

But the highlight of the evening occurred with Diana served up a show-stopping rendition of her soaring 1970 Motown classic “Ain’t No Mountain High Enough.”

“Diana was smiling from ear to ear all night,” the insider tells PEOPLE. “You could tell she thought it was a great birthday celebration.”