When it comes to Cameron Diaz, Benji Madden has always known she's the one.

So on the actress's 51st birthday, the Good Charlotte rocker resurfaced on social media and expressed how much she means to him.

"I'm off line mostly these days, just working, painting, making things and doing family life, but I have grown to like my little tradition of coming back on special occasions to show love to my Queen," Benji—who shares 3-year-old daughter Raddix with Cameron—wrote on Instagram Aug. 30, "so today, it's a very Happy Birthday to my beautiful wife, best friend, best partner in everything, ride or die, greatest Mom to our little girl, @Avaline wine boss, family chef, advisor, collaborator and everything else. You do it all."

And he's thankful for her and the life they've built together. 

"So grateful to have our family and I am one lucky man - I know that seems obvious but it really is nice to say it out loud now and then when you're feeling it," the musician added in the post, which also featured a photo of Cameron holding a cat and smiling from ear to ear. "I love you forever always yours true love Happy Birthday Cameron."

Needless to say, The Holiday star—who tied the knot with Benji in 2015—appreciated the message and sent the love right back. 

"There's no one else I would rather do this life with," she commented. "We are so blessed.. I you with all my [heart]."

Of course, the sweet shout-out should come as no surprise to fans. After all, Benji and Cameron have let their feelings for each other be known and given followers glimpses into their romance both in birthday, wedding anniversary and Mother's Day posts as well as in interviews.

"He's just the guy who I can totally count on," the Charlie's Angels alum said on a March episode of Michelle Visage's Rule Breakers podcast. "He's hilarious, and he's so funny, and he's the best dad ever. I could cry, he's just the best."

To look back at Cameron and Benji's love story, keep reading.

One month before tying the knot, Cameron Diaz flashed what appeared to be an engagement ring from Benji Madden. 

Surprise! The two tie the knot at the actress' Beverly Hills home.

Benji gets a tattoo of his Cameron's name on his chest.

The There's Something About Mary star opens up on Andy Cohen's Radio Andy show about how she and Benji met.

"The first thing I said when I first met my husband was, 'He's hot,'" she says. "How come I didn't know this before? We had never been in the same circle."

Cameron adds that they formally met when she hosted a dinner party at her house with his brother Joel Madden and sister-in-law Nicole Richie. Joel asked if he could invite Benji. Cameron says, "Then I saw him again. Wait a second, still hot!" 

The two vacation in Italy again.

"Getting married to him was the best thing that ever happened to me," she tells InStyle about Benji. "My husband's the best. He's the greatest human being, and he's my great partner. Marriage is certainly hard, and it's a lot of work. You need somebody who's willing to do the work with you, because there's no 60-40 in marriage. It's 50-50, period. All the time."

Cameron and Benji announce on Instagram that they have welcomed a baby girl, Raddix Madden.

"I'm off line mostly these days, just working, painting, making things and doing family life, but I have grown to like my little tradition of coming back on special occasions to show love to my Queen," Benji wrote on Instagram. "so today, it's a very Happy Birthday to my beautiful wife, best friend, best partner in everything, ride or die, greatest Mom to our little girl, @Avaline wine boss, family chef, advisor, collaborator and everything else."

For the latest breaking news updates, click here to download the E! News App