The 26-year-old put the hosts in front in the 48th minute. Samuel Castillejo found the striker on the right and he held off his marker before unleashing an unstoppable effort into the roof of the net.
Mario Gaspar made it two with a clever finish that beat Leandro Chichizola at his near post in the 65th minute before Ximo Navarro scored an own goal two minutes later to make it three to the Yellow Submarine.
Second half substitutes Nicola Sansone and Denis Cheryshev combined as the former added a fourth with the last kick of the game.
Bakambu who scored his eighth league goal in nine appearances this season was replaced by Sansone in the 71st minute after a collision with Chichizola left him struggling with a knock.
This win sees Javier Calleja’s side move up to fifth on the Spanish top flight log and will they will visit the Wanda Metropolitano to tackle Thomas Partey’s Atletico Madrid on October 28.