Barcelona thumped Cadiz 4-0 to move atop of the LaLiga table in a game that was halted for about 50 minutes following a medical emergency in the stands.
De Jong got the breakthrough in the 54th minute while Lewandowski came off the bench to double the lead in the 64th minute to put Barcelona on the driving seat. The Poland forward has now scored nine goals in six appearances since his summer move from Bayern Munich.
The visitors held onto the lead with less than 10 minutes on the clock, when a fan had medical emergency in the stands and the game had to be stopped and players taken off as a result.
The game resumed after close to 50 minutes but Barcelona were still in the mood — they switched on again and added another two goals to annihilate the home side.
Substitute Ansu Fati added a third while Dembele rounded off the scoring in the dying embers to mark an impressive win for the Catalans.