Gignac, who shocked many in the football world when he snubbed European clubs to join Tigres in June, opened the score in the 14th minute.
Midfielder Javier Ignacio Aquino doubled the score in the 28th minute while Gignac was involved in the third goal in the second half, as his volley was blocked by the keeper only to land at the feet of Brazilian winger Rafael Sobis, who did not miss.
Gignac has now scored 14 goals in the Apertura-2015 championship and his team is well placed to win its fourth title when they play the return leg in Mexico City on Sunday.