After a goalless first half, the Mexicans scored four goals inside 12 minutes early in the second and sent out a clear message they will not surrender their CONCACAF crown without a fight.
Hernandez's goals were hardly among the classiest he will score but they were another reminder that the 23-year-old, who scored 20 goals in all competitions in his debut season for Manchester United, is becoming one of the sharpest poachers around.
It was also the perfect gift for the massive Mexican-American crowd that turned out to welcome 'El Tri' to Texas.
“It’s unbelievable, the support that we have from Mexicans who live here,” Hernandez told reporters. “You can see it here - 80,000 people and most of them in green shirts and it means a lot to us.
“The most important thing for me is the three points, I don't care if I score, sometimes I won't -- the main thing is we won,” said the striker.
Hernandez and Mexico should have found their way on to the scoresheet in the first half but they looked hurried and anxious in front of goal, but once the first goal went in, they never looked back.
El Salvador's defence was ripped open far too easily and their coach Ruben Israel will have a tough job to get his team to bounce back for their next game in Group A against Costa Rica on Thursday.
In the final minute, Hernandez was brought down in the area by Marvin Gonzalez, who was sent off, and the little forward rose to convert the spot kick.
He did so with the coolest and cheekiest of chips, signing off with a clear signal of his confidence.
