Foster, 68, and McPhee, 33, spent Sunday together at the Elton John AIDS Foundation Academy Awards viewing party sponsored by Bulgari.
Although the pair didn’t walk the red carpet together, they were all smiles as they posed side-by-side inside the event.
The American Idol alum looked chic in a semi-sheer lacy black dress. The Grammy-winning producer was also dressed for the occasion, wearing a classic black suit with a partially unbuttoned white shirt underneath.
Although McPhee and Foster have yet to comment publicly on their relationship, the musical pair first sparked romance rumors in September 2017, after the latter’s daughter Erin Foster shared photo of them together in Los Angeles.
While McPhee and Foster have been friends for years — first meeting on the set of American Idol when McPhee was a contestant in 2006 — Erin captioned the photo, “Excited about my new step mom.” (A source close to the situation told PEOPLE at the time that the social media posts were a joke.)
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Asked about the relationship rumors, McPhee previously told PEOPLE that she had “zero desire” to address them. “It’s great that they want to do that. I think it’s so amusing that people are amused by my love life,” she added.
“Here’s how I look at it: I’m not doing anything wrong, so whether people think it’s true or false, I don’t, you know, there’s nothing bad happening in my life, so people can just say whatever they want,” she said.
The 2018 Oscars were held at the Dolby Theatre at Hollywood & Highland Center on March 4 and were telecast live on ABC.