Tarnawa struck Group One gold for Dermot Weld in the Prix Vermeille at ParisLongchamp.
The Aga Khan-owned filly won at Group Three and Group Two level in 2019, and made a successful return to action when winning the Give Thanks Stakes at Cork for the second season running last month.
With Give Thanks runner-up Cayenne Pepper impressing in the Blandford Stakes at the Curragh earlier in the afternoon, Tarnawa was a 5-1 shot for her French assignment, with Jean-Claude Rouget’s Raabihah all the rage as the 5-6 favourite.
Ridden by Christophe Soumillon, Weld’s charge travelled with zest for much of the mile-and-a-half contest before throwing down her challenge in the home straight.
Tarnawa displayed a bright turn of foot inside the final two furlongs and was ultimately well on top at the line.
Raabihah made late gains to fill the runner-up spot, just ahead of Ed Vaughan’s Dame Malliot, who ran a fine race from the front under Frankie Dettori.
Weld was represented on course by his son Mark, who told Sky Sports Racing: “It’s absolutely fantastic – she’s a wonderful filly. Thank you so much to His Highness the Aga Khan, his family and all his team.
“This is a very prestigious race. She’s a very good filly and deserved the step up to a Group One.
“She was very impressive last time at Cork, so we were hopeful.”
Whether Tarnawa returns to Paris next month for either the Prix de l’Arc de Triomphe or the Prix de l’Opera is up for discussion.
Weld added: “I’ve spoken to my father and we have to talk to the Aga Khan’s team. Today was the day for now, but she was so impressive, so it (Arc) is a possibility.”
Dermot Weld said from the Curragh “It was always the plan to have an autumn campaign with her.
“When she came back to me from Giltown Stud she was in great condition and she won the Group Three from Cayenne Pepper (who won the Blandford) which was a real performance and it was a beautiful performance today.
“I purposefully targeted the second half of the year. I’ll speak to His Highness the Aga Khan and Pat Downes (racing manager) and we’ll come up with a plan for her.”
Despite the reverse, Rouget was not ruling anything out for Raabihah.
He said: “She ran well, but now she is against tougher rivals. She is changing category, she has proved that she is the best three-year-old filly in France.
“We will see how she is over the next two weeks, but if she is well in herself she will run in the Arc.”