Brown Butterfly surged clear in the final furlong of the seven furlong fillies maiden at Naas to score for Kevin Prendergast and Declan McDonogh at odds of 13/2.
The winner, in first-time blinkers, wore down long-time leader Ballroom to win by an impressive four-and-a-half lengths from Aidan O'Brien's charge.
“We dropped her back in trip and put a set of blinds [blinkers] on her,” Kevin Prendergast explained.
“At the Curragh she was too free over a mile and a quarter and didn’t get home. Her pedigree says she should get a mile and a half but apparently she doesn’t.
“I was hoping she would run well but didn’t think she would win. She could run in a mile handicap in four or five days time off a rating of 72.”
Jim Bolger’s Advenio was sent off the 2/1 favourite but never landed a blow trailing in sixth of the seven runners.