Sofia on the cover of Shape Magazine for March.

“If I walk outside without lipstick, I feel naked,” the actress, 38, tells the March issue of Shape, in which she’s named the sexiest woman in Hollywood. Her fave body part? “I’m sure men would tell you it’s my boobs, but I like my eyes,” she tells the mag. “They have a natural cat’s-eye shape, so I try to play that up.”

The New Year’s Eve actress is just as diligent when it comes to maintaining her famous hourglass shape.

Of her frequent workout sessions with trainer Gunnar Peterson, she says, “Oh, I hate it! But I also know that at my age — I’m almost 40! — I have to do it to maintain my figure. When I can, I try to do Latin dancing for exercise because it’s so much fun and I just love the music. Two hours before I go [to the gym], I’m already wishing it was over. I psychologically fool myself into believing it’s part of my job.”

And while the 5-foot-7 star says she gets meals from diet delivery service Freshology when she’s looking to drop a few extra pounds, she’s certainly not looking to get super skinny.

“I think when women reach a certain age, they look better with a little fat in their face,” she tells the issue. “I’m lucky I’m Latin because people expect me to be a bit more plump.”