The 26-year-old striker opened the scoring for the hosts in the 25th minute. Manuel Trigueros played the striker through on goal and the former Bursaspor man lobbed the ball over goalkeeper Mariano Barbosa.
The Congolese forward doubled the lead for his side in the 52nd minute, off a Nicola Sansone cross. Bakambu completed his treble from the penalty spot after Anaitz Arbilla fouled Samuel Castillejo in the area.
Javier Calleja’s side pick up their third win of the season which saw them rise to ninth in the Spanish topflight standings. They travel to Estadi Montilivi to take on Girona on October 15.