The player got his second card after he kicked the ball away after the referee had whistled for an infringement.
Sowah had attempted to waste more time for his Belgian club to leave Spain with a point in their goalless game against Atletico Madrid.
Kamal Sowah has two goals in the Champions League after scoring his first goal in the competition in a 4-0 win over Porto and got another goal against Atletico Madrid in the first leg.