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Dear Cameron Diaz: Is that a ring we see on THAT finger?

The "Sex Tape" star is setting off rumors of a possible engagement after she was seen twice on Wednesday donning what appeared to be a diamond sparkler on her left hand.

First, Cam was spotted wearing the diamond ring at the Hollywood Costume Luncheon, where she waved with her left hand, appeared beaming and made no effort to conceal the hand. Later, she was spotted wearing it at a romantic dinner with her boyfriend, Good Charlotte rocker Benji Madden.

RELATED: Cam cuts interview short over Drew Barrymore questions

The couple have been together since April after apparently being set up by Madden's sister-in-law Nicole Richie.

For his part, the 35-year-old rocker recently told Details Magazine that he's better at relationships now than he was in his past.

RELATED: Cam and Benji visit her family in Florida

"I did relationship damage to myself in my 20s. That's what your 20s are for," he said. "You learn, and then you apply it in your 30s."

In the same interview he said that having a family is secretly what every man wants.

He may have some convincing to do with his lady.

RELATED: Cam on infidelity: Everyone will be cheated on

In July, Cameron told Esquire Magazine that children are not exactly on her mind.

"It's so much more work to have children," the actress told the magazine. "To have lives besides your own that you are responsible for, I didn't take that on. That did make things easier for me."

She continued, "A baby, that's all day, every day for 18 years. Not having a baby might really make things easier, but that doesn't make it an easy decision. I like protecting people, but I was never drawn to being a mother. I have it much easier than any of them. That's just what it is. Doesn't mean life isn't sometimes hard."