The E! TV host, 37, showed off her massive diamond ring as she and fiancé Keven Undergaro arrived back at Los Angeles International Airport on Friday after their romantic (and busy!) week in New York City.
Menounos' "bright and chic" custom-created sparkler stood out against her simple white T-shirt, black jacket and jeans. Undergaro coordinated with his longtime love in a black tee and jeans.
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"Although I said that this isn't a proposal, I want to ask you something," Undergaro said as he got down on one knee. "Will you make me the happiest man on Earth?"
Jeweler Jean Dousset helped Undergaro design the perfect ring for Menounos, who has been dating Undergaro since April 1998.
"[Keven] and I first spoke on the phone and I consulted on what I thought Maria's ring should be (about her!) and shouldn't be," Dousset told PEOPLE. "We then met to begin the design process [which took] one month total. We had a limited amount of time and worked together closely to create the perfect ring for Maria."
He added: "We imagined what the ring should be based on her personality and style. Bright and chic."