The striker's effort helped The Canaries to a 3-0 triumph at Stade de la Mosson.
It was his first goal for the club since completing a loan move from Portuguese giants Porto in the summer.
More importantly, it was his maiden career goal in all competitions since scoring for former club Lorient in December 2017.
Kalifa Coulibaly opened the scoring in Tuesday's game, putting the ball at the back of the net in the 58th minute after being set up by Charles Traore.
Waris then made the score 2-0 for the away side with a cool finish in the 80th minute, before Emiliano Sala netted the final goal in stoppage time.
The win takes Nantes through to the fourth round of the League Cup.