Jennifer Aniston, Justin Theroux and Courteney Cox
PictureGroup; Wireimage; Startraks
08/29/2012 at 03:00 PM EDT
If you wanna be my lover, you gotta get with my Friends
and fiancé Justin Theroux
stepped out for a cozy dinner with Courteney Cox
at the Sunset Tower Hotel's Tower Bar on Monday.
"Jennifer looked adorable!" an onlooker tells PEOPLE. "She looked so pulled together and very chic. She was dressed casually, but in heels."
Aniston recently returned to L.A. during a break from filming We're the Millers in North Carolina with Jason Sudeikis
"They were very calm and carrying on a regular dinner conversation," the source adds. "Jennifer had a big smile on her face. She and Justin both looked very happy."
It was the first time Aniston and Theroux have been seen out together since their Aug. 12 engagement
The Sunset Tower holds fond memories for the couple. It's where Aniston and Theroux were first spotted out together publicly
when they shared a three-hour casual dinner back in May 2011.
After dinner, the trio greeted designer Tom Ford
, seated at a nearby table with Tom Hanks and Rita Wilson
– who double dated with Aniston and Theroux
last April – and several others. Ford was celebrating his 51st birthday.
– Paul Chi