Justin Theroux and Jennifer Aniston split in 2017 after two and a half years of marriage

Justin Theroux just gave his ex Jennifer Aniston the sweetest shoutout.

The 47-year-old actor shared a black-and-white photo of Aniston, who turned 50 on Monday, carrying a horned statue above her head as she gazed down at the camera.

“Happy Birthday to this fierce Woman,” Theroux wrote in the caption. “Fiercely loving. Fiercely kind. ….and fiercely funny. ❤️ you B.”

The two actors began dating in 2011 and married in 2015. The pair split at the end of 2017.

“In an effort to reduce any further speculation, we have decided to announce our separation,” they said in the statement in February 2018. “This decision was mutual and lovingly made at the end of last year. We are two best friends who have decided to part ways as a couple, but look forward to continuing our cherished friendship.”

The Leftovers actor broke his silence on their breakup in September 2018, telling The New York Times there was no hostility between them.

“The good news is that was probably the most — I’m choosing my words really carefully — it was kind of the most gentle separation, in that there was no animosity,” he said.

Theroux added, “Again, neither one of us is dead, neither one of us is looking to throw hatchets at each other. It’s more like, it’s amicable. It’s boring, but, you know, we respected each other enough that it was as painless as it could be.”

Still, Theroux said, “It was heartbreaking, only in the sense that the friendship would not be the same, as far as just the day to day. But the friendship is shifting and changing, you know, so that part is something that we’re both very proud of.”

For her part, Aniston said her past marriages to Theroux and Brad Pitt were “very successful” during an interview with Elle magazine for its January 2019 issue.

“I don’t feel a void. I really don’t,” she said. “My marriages, they’ve been very successful, in [my] personal opinion. And when they came to an end, it was a choice that was made because we chose to be happy, and sometimes happiness doesn’t exist within that arrangement anymore.”

Pitt, 55, even attended her star-studded birthday bash Saturday. Some of her closest friends also attended included former Friends costar Courtney Cox, George and Amal Clooney, Gwyneth Paltrow, Robert Downey Jr. and more.

The 21st Annual Critics' Choice Awards - Red Carpet
Jennifer Aniston and Justin Theroux
| Credit: Christopher Polk/Getty

Aniston has been focusing on her work, including her upcoming Apple series, which she is executive-producing alongside Reese Witherspoon.

“Jen has always been a hard worker and a perfectionist when it comes to filming,” a source previously told PEOPLE.

The insider added the actress shows her appreciation for the cast and crew, which includes Witherspoon, Steve Carell, Billy Crudup, Mark Duplass and Gugu Mbatha-Raw.

“She often caters special treats for the crew and is always the first one to thank everyone for their hard work,” the source continued.

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Based on journalist Brian Stelter’s book Top of the Morning: Inside the Cutthroat World of Morning TV, the show will follow the dynamics and drama involved with producing a morning show. It’s been picked up by Apple TV for two seasons, or 20 episodes.

The actress also filmed an upcoming Netflix movie with pal Adam Sandler and released the streaming site’s coming-of-age-drama Dumplin’.

As a source previously told PEOPLE, “She isn’t concerned about dating. She is happy to focus on work.”