The French striker, a £30 million acquisition from Lyon, replaced Ronaldo at half-time at the Tallaght Stadium and the former Lyon forward scored with just three minutes remaining to break the home side's hearts.
Ronaldo's every touch was booed by the 10,915 fans squashed into Rovers' Tallaght Stadium, where capacity was trebled to see Real's Galacticos who had trained for a week on the outskirts of Dublin.
Some tried to catch a glimpse of the world player of the year from nearby apartments, many with 190,000 euro for sale signs attached, roughly what Real's new number nine earns a week.
The Spanish giants lined up with the likes of Raul, Gonzalo Higuain and Guti from the start, although the first of the club's major summer signings, Kaka, was granted extra holiday following his triumphant Confederations Cup campaign with Brazil.
However, all eyes were on £80m world record signing Ronaldo making his debut, but the Shamrock players treated him to a taste of what it is like playing week in week out in the League of Ireland as Rovers centre-half Pat Flynn sent the winger clattering to the floor after his first touches had sent him speeding past defenders in trademark style.
Left-back Marcelo came close for Real in the sixth minute, shooting from just outside the box with his right foot, forcing goalkeeper Barry Murphy to deflect the ball out for a corner.
