Barcelona continued their perfect response to last weekend's Clasico defeat thanks to goals from Dembele, Sergi Roberto, Robert Lewandowski and Ferran Torres.
In truth, the game was decided inside the first quarter of the match as Barcelona raced into a 3-0 lead courtesy of an 11-minute spell that their visitors were unable to deal with. Dembele - who was involved in all four goals - got the ball rolling as he finished off Lewandowski's cross with a somewhat surprisingly well-taken header.
Once he had scored the opener, he was keen to take on the role of provider and that started by laying off the ball for Roberto who raced into the penalty area and - courtesy of a rather fortunate deflection - made it 2-0. Lewandowski was then the beneficiary of Dembele's hard work as he latched onto the perfect through ball before taking a brilliant first touch and emphatically finishing past a helpless Unai Simon.
While Barcelona's pressure waned somewhat following the injury and subsequent withdrawal of Gavi, they were still in total control of proceedings throughout the 90 minutes. That control led to a fourth goal fairly late in the second half as Dembele, once again, took on a host of opposing defenders before picking out Torres expertly inside the penalty area and he made no mistake, sliding through the legs of Simon and into the back of the net.
Read below for GOAL's winners, losers and Barcelona player ratings on a brilliant night at Camp Nou.