Christina Aguilera spoke to PEOPLE about their birthday plans
Credit: Kevin Mazur/Getty

Christina Aguilera dedicated a song to her fiancé Matthew Rutler Saturday night as they celebrate the first birthday of their daughter Summer Rain.

The 34-year-old star held a crowd of Hollywood superstars, potential U.S. Presidents and industry big-wigs spellbound as she performed at the hot-ticket event of the evening – Apollo in the Hamptons.

She took to the stage at billionaire philanthropist Ron Perelman’s East Hampton, New York, estate, The Creeks.

Baby Summer Rain celebrates her birthday on Sunday and after belting out hits like “Lady Marmalade” and “Ain’t No Other Man,” Aguilera told the crowd – which included Jack Nicholson, Jimmy Fallon, Mary-Kate Olsen, Chris Christie, New York Mayor Bill de Blasio and Bethenny Frankel – that the weekend was an important one for her.

“This is a special weekend, it’s my first daughter’s first birthday,” she said.

Aguilera then dedicated a song to Summer Rain’s father, Rutler, before singing Etta James’ “At Last.” The couple have been engaged since Valentine’s Day 2014.

Speaking to PEOPLE, Christina, who had flown in from Los Angeles to help raise money for education programs at Harlem’s Apollo Theater, was clearly looking forward to her daughter s birthday.

“We’re going to celebrate today as a family and have a little party later in the month. She’s so beautiful.”

She stayed to enjoy performances by Jamie Foxx – who pulled Jimmy Fallon up onstage for a singalong – Smokey Robinson, who sang a duet with Jon Bon Jovi; Pitbull; Emeli Sandé and the Roots.