The 28-year-old was level on six with Etoile’s Baghdad Bounedjah and Georges Ambourouet of CF Mounana, who were knocked out early in the competition.
Bounedjah was injured early in the second leg, while Gabuza failed to find the back of the net, meaning there is a three-way tie for the award.
Kermit Erasmus, who started the day on five goals, also missed his chance to join the top dogs.
Ammar Jemal, who scored the decisive goal in Sousse yesterday, also finished with five goals.