Cristiano Ronaldo capped a magnificent display with the match-winning goal as Portugal powered past Czech Republic and into the semi-finals of Euro 2012.Ronaldo, who scored twice against the Netherlands, hit the woodwork in each half with fine strikes.And he finally found the net with 12 minutes remaining, thumping a header into the ground and beyond Petr Cech.Czech Republic failed to muster a shot on target as they rarely threatened throughout a tense evening.Portugal will now face Spain or France for a place in the final, and with arguably Europe's best player beginning to show his very best form, they could take some stopping.The Real Madrid forward was instrumental in guiding Portugal through Group B, putting a sloppy display against Denmark behind him to score both goals against the Netherlands on Sunday.And after a slow start to this quarter-final in Warsaw, the world's most expensive player grew in stature to dominate the action in impressive fashion.Czech Republic enjoyed a strong opening 15 minutes, with right-back Theodor Gebre Selassie initially effective in a man-marking role on Ronaldo, but once the former Manchester United man threw off his shackles and began to roam in a free role he lit up proceedings.He had already been harshly penalised by referee Howard Webb when running through the middle of the defence before striking the post after a moment of genius.Ronaldo controlled Raul Meireles's long pass on his chest, turned defender Michal Kadlec effortlessly and beat Petr Cech with a shot that thundered against the base of the post and rebounded to safety.He hit the post again - the fourth time in four games he had struck the woodwork - after the break with a trademark dipping free-kick from 30 yards as Paulo Bento's side mounted a siege on Cech's goal.Substitute Hugo Almeida then saw a header correctly ruled out for offside and also wasted two further efforts before the breakthrough came - inevitably - from Ronaldo.The impressive Joao Moutinho broke from midfield down the right before standing up a cross to the back post.Ronaldo met the cross with a fierce header which bounced down and then into the roof of the net for his third goal of the tournament.It was his 66th goal for club and country in an incredible season.Michal Bilek's Czech side had shrugged off a 4-1 thrashing at the hands of Russia in their opener to reach the last eight, but, again shorn of injured captain Tomas Rosicky, they looked limited going forwards and never tested Rui Patricio in the Portuguese net on their way to a limp exit.In contrast, Portugal will move on confident of reaching a second European Championship final in three tournaments, knowing that in Ronaldo they unquestionably possess the most potent weapon in European football.