She's Liza with a "Z" and she's not about to let anyone forget it.

Liza Minnelli dazzled the crowd gathered for Michael Feinstein's special concert at the Arboretum in Los Angeles over the weekend when she joined him for a surprise performance of "Our Love Is Here to Stay." Feinstein is the principal conductor for the Pasadena Pops, though on Saturday he put down the baton and performed the concert devoted to Gershwin. Minnelli, coincidently, is the goddaughter of Ira Gershwin.

"Liza wanted to make an appearance and perform with Michael in celebration of his newly announced venture at Café Carlyle in NY," a source close to Minnelli and Feinstein tells EW. "The two are the very best of friends and the audience could see their mutual affection shining through during their performance."

In videos taken by the audience and shared to social media, like the one below, Minnelli can be seen in a director's chair singing the song and getting a standing ovation upon its completion.

Minnelli, who has largely stepped back from public life in recent years, was most recently publicly seen on stage at the Oscars, escorted in a wheelchair by Lady Gaga. At Gaga's insistence, the duo presented Best Picture together, with the latter dressed in a Cabaret-inspired tuxedo. At the appearance over the weekend, however, Minnelli walked out onstage without her wheelchair.

"Oh, I'm so excited. I haven't been up here in so long. I love you. Thank you for all the years of joy that you brought me," Minnelli exuberantly told the crowd when she was seated in a director's chair. The iconic singer and Feinstein immediately burst into song from there, and she received rapturous applause at the song's end.

Feinstein, an acclaimed musician and Ambassador of the Great American Songbook, and Minnelli have been friends for many years. At the concert on Saturday, Minnelli greeted Feinstein with a hug and kiss and called him her "dearest friend in the world."

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