Robert Lewandowski produced a striker's masterclass as he scored four goals against Real Madrid in a commanding Champions League semi-final first-leg victory for Borussia Dortmund. The Poland striker volleyed in Mario Gotze's cross at the back post early on before Cristiano Ronaldo tapped in. Lewandowski collected Marco Reus's shot to poke in past Diego Lopez and crashed home a 12-yard strike for a hat-trick. The 24-year-old converted his fourth from the spot, after Reus was fouled. With his contract due to expire at the end of next season, the forward has been a reported summer target for Manchester United and Bayern Munich. And his value will increase no end after he became the first player to score four times in a Champions League semi-final. His ruthless display of finishing continued Dortmund's 100% European home record this season and leaves Real Madrid with a mountainous task to reach the final at Wembley in May. It also showed more evidence of a shift towards German dominance of Europe, only 24 hours after Bayern Munich beat Barcelona 4-0 in their semi-final first leg. Bayern's thrashing of Barca came on the same day they announced a £31.5m deal for Gotze, but Dortmund's response was an energetic display that left them on the verge of a first Champions League final appearance since 1997. Boss Jurgen Klopp had issued a rallying call to the club's fans urging them to be positive in their support despite the Gotze development. And the effervescent coach received a similarly rousing performance from his team as they set off at a blistering pace and could have been a goal up a minute before Lewandowski's opener. Reus, who was a constant thorn in the Real Madrid side, took on the visiting defence but his shot was saved by Diego Lopez, with Lewandowski failing to tuck in the rebound. The Pole made amends after eight minutes when he shook off the attentions of Pepe to steer in Gotze's delicious cross at the back post. This was Real's third consecutive Champions League semi-final under boss Jose Mourinho, having lost the previous two, and the game's pattern looked ominous for his side as Dortmund tore into them at every opportunity with Sven Bender quick to dispossess his opponents in midfield. The Spanish side were limited to shots from Ronaldo and Xabi Alonso, but the game appeared to have turned in the space of a minute just before the break. Reus again bore down on the Real back line and looked like he was tripped in the penalty area by Raphael Varane, yet referee Bjorn Kuipers waved the German's appeals away. The visitors then pounced as Mats Hummels' poor back pass let Gonzalo Higuain break free of the defence, and his cross allowed Ronaldo a simple tap in for his 50th Champions League goal. Dortmund replied with the resolve that has won them new fans this season. They regained the lead five minutes after the break as Lewandowski latched onto Reus's shot to put the hosts back in control. More impressive was his third goal five minutes later. It came from another mis-hit shot, this time from left-back Marcel Schmelzer, whose effort cut across the penalty area, but the Polish striker took a touch to kill the ball, dragged it out of Pepe's reach and smashed an unstoppable shot into the top corner. Echoes of Bayern's pummelling of Barcelona on Tuesday were already in mind and it got worse for Mourinho's side as Xabi Alonso bundled Reus over in the penalty area, with Lewandowski making no mistake from the spot. Ronaldo went close to pulling another goal back but Roman Weidenfeller was quick off his line to thwart the Portuguese forward on a deflating night for the Spanish league champions.