Coming off a pair of losses with Mexico, Dos Santos turned in a strong performance for the Yellow Submarine.
Gareth Bale scored on his debut with Madrid in the first half, canceling out Cani's opener. After Cristiano Ronaldo restored Madrid's lead in the 64th minute, Dos Santos provided the equalizer five minutes later.
Cani's shot was only parried by goalkeeper Diego Lopez and the rebound fell to the Mexican international, whose powerful shot was deflected by Lopez but settled in the bottom corner of the net.
The goal was the third in four games for Dos Santos in league play with the Yellow Submarine.