The Ken and Bev Kelso-trained five-year-old powered home from the back of the field to win the Listed Team Wealleans Matamata Cup (1600m).
"She got a long way off them and I was a bit concerned, it was a big effort," Ken Kelso said.
"Bev made the comment the other day that she could be the best mare we've had."
Successful when resuming over 1200m at her previous appearance, Cote d'Or settled in the last four before mounting a run across the top and she rounded off strongly in the run home.
"She's very, very smart," Kelso said. "She's just little, but she's a bulldog. She's very competitive."
Kelso is unsure where the mare will head next and said he would discuss her immediate future with owner Sir Peter Vela's racing manager Garry Cossey.
Bred on the same Makfi-Zabeel cross as the multiple Group One winner Bonneval, Cote d'Or completed a winning double for Sir Peter Vela following the earlier success of Sleeping Beauty.
She comes from one of Pencarrow Stud's best families being a half-sister to Group winners Dolmabache and Pure Elegance from Our Echezeaux, who comes from the family of Ethereal and Darci Brahma.
Cote d'Or's regular rider Danielle Johnson was full of praise for her mount, who she believed can make her mark at the top level.
"They left us quite flat-footed but we got on the back of the three wide train and she finished off really well. She's good and she's still got so much to learn as well."
Longshot Big Dreamer ran home strongly from midfield to finish runner-up ahead of Tessastock and Eleonora made an encouraging return with her effort for fourth.
Last season's Gr.3 Ethereal Stakes (2000m) winner and Gr.1 VRC Oaks (2500m) placegetter, Eleonora was having her first start since claiming the Gr.3 Sunline Vase (2100m) in March. – NZ Racing Desk.