Before a sellout crowd of 52,000 at November 7th Stadium the midfielder's strike gave his side a 2-1 victory on aggregate over the home club Sfaxien and also put the club in an elite group of three teams to ever successfully defend the title.
The goal was a devastating blow for first time finalists Sfaxien who were just moments away from lifting the trophy after their away goal in the first leg looked to have been enough to secure the title in front of their home fans.
To add insult to injury the Tunisian side was robbed of a goal soon after half time when Tarek Ziadi had the ball in the back of the net only to be ruled offside despite replays showing the assistant's referees error.
Sadly, the game may be remembered for a number of dubious decisions the assistant referee from Benin made during the showpiece of African club football.
Mohamed Abou Tarika celebrates
With the seconds counting down, the title seemed destined for Tunisia until Aboutraika struck and triggered a mass exodus from the ground.
It was a heart-breaking climax for Sfaxien, making only their third appearance in the Champions League and who were eliminated by the other Cairo giants, Zamalek, in the 1984 and 1996 editions.
However, the controversy meant little to the Red Devils who celebrated matching their local rival's five titles while also pointing to the fact that the victory came without six players who were missing through injury and suspension.
Before the match, the odds were against Al Ahly as only four of 15 previous African Champions League finals in which the first leg was drawn ended in victory for the club playing away second.
Merdassi had a great chance early for the home side when with 28 minutes gone he headed an inviting cross wide with the Ahly defence in disarray.
Ahly coach Manuel Jose, a gum-chewing Portuguese veteran of many African Champions League campaigns, replaced cautioned Ghanaian midfielder Akwety Mensah with striker Emad Moteab just before half-time.
The move signalled a desire to attack more only for Sfaxien to come out of the blocks faster in the second half and while Ziadi sportingly accepted the offside ruling, spectators watching video replays howled in protest.
The victory also earned Al Ahly the final place at the FIFA Club World Cup in December.