Cannes 2012: Kristen Stewart Steps Out in Stunning Scarlet Reem Acra Gown

Cosmopolis Premiere Kristen Stewart Split - P 2012
Getty Images

Cosmopolis Premiere Kristen Stewart Split - P 2012

The actress fulfilled her brand ambassador duties with a Balenciaga gown Monday but pulled out all the stops at the "Cosmopolis" premiere.

Kristen Stewart definitely saved the best for last. After she wore a Balenciaga print gown for the Cannes premiere of On the Road on Wednesday night, we thought she couldn't top the scrollwork print dress designed by Nicolas Ghesquiere.

PHOTOS: Cannes Day 8: 'On the Road' Photocall, '7 Days in Havana' With Benicio del Toro

We were wrong. The winner was her bright crimson Reem Acra (pre-Fall 2012 ) crepe gown -- majorly sexy both coming and going with a very deep V neckline and a sheer lace back -- worn at Friday's premiere of Cosmopolis.

But like a good movie star, Stewart avoided being photographed with her boyfriend, Twilight co-star Robert Pattinson, who toplines the new film by David Cronenberg. Instead she posed with her arm around Road co-star Tom Sturridge, who is dating actress Sienna Miller.

We don't know how Pattinson fared on the carpet, wearing his slick Gucci suit, but he definitely had trouble keeping a straight face at the Cannes press conference earlier.

According to Dana Kennedy, a reporter based in the South of France, the famous leading man/sex symbol acted more like a goofy, silly 11-year-old as he tried to answer questions from the international press. “He giggled throughout the press conference, frequently whispering to Cronenberg and erupting into more self-conscious laughter.”

STORY: 'On the Road' Stars Kristen Stewart, Kirsten Dunst vs. Milla Jovovich in a Red Carpet Showdown

Cronenberg nixed any suggestions that Cosmopolis character, Eric Packer, who spends most of his time in his coffin-like sretch limo be compared to Pattinson's life in a fishbowl as a result of his teen idol status or his Twilight vampire role ...

"The character of Eric Packer is a real person with a real past and it is Cosmopolis, not Twilight," Cronenberg told reporters.