Blues went into the game in Belfast on a real high after the historic victory over Toulon in the Heineken Cup. But found themselves up against an Ulster team also brimming full of confidence after defeating Leicester Tigers and Montpellier in Europe.
First half tries from Dan Tuohy and Jared Payne underlined that fact and gave Ulster the early initiative before Robin Copeland broke tackles and galloped over to reignite the Blues’ bid.
Luke Marshall scored a minute into the second half to halt growing Blues pressure and a yellow card to Copeland made the visiting task that little bit harder.
Back came battling Blues once more and a well worked score, when down to 14 men, allowed wing Richard Smith to celebrate his first start of the season by crashing over in the corner.
However, a try from Irish wing Andrew Trimble secured the try bonus point for Ulster and a last minute score from Tuohy – as Blues looked to run from deep - wrapped up the win for the hosts.
Ulster were on the crest of a five-game winning streak and went straight onto the front foot as flanker Robbie Diack looked to exploit an overlap on the left before being hauled down by Harry Robinson.
Home full back Stuart Olding, called up for a start, then tried to jink his way around tackles but was halted by the sniping Josh Navidi.
The home side applied huge pressure at the first scrum of the game to win possession back and then, on the second scrum, won a penalty that fly half Paddy Jackson slotted for the opening points of the night.
Back came Blues and the first away attack of the evening allowed Filo Paulo and Smith the opportunity to attack the gain line at pace before Lloyd Williams popped up at the base and won a penalty, as Ulster failed to roll away, that Halfpenny nudged over.
Cory Allen had to be alert to pick up Tommy Bowe’s grubber kick after turnover ball before Ulster exploited a big gap in midfield as Olding cleverly delayed his pass wide and sent Luke Marshall away with Tuohy eventually the player on the end of the overlap to touch down.
Slick hands from Blues almost produced an immediate response as they moved the ball wide at pace and Copeland kicked ahead into space. He then showed his pace to charge down the clearing kick from Olding, but the ball ran away from the Number Eight and safe.
More home possession saw Bowe once again kick in behind and when Robinson failed to gather on the greasy turf the ball fell into the hands of Halfpenny who mopped up under mounting pressure and Rhys Patchell kicked clear.
Ulster were enjoying success at scrum time and when they won another penalty they opted to take a quick tap and go with devastating effect.
The ball was spun wide by the orchestrating Pienaar and a marauding Payne had too much time and space as he flew over in the left corner to open up a commanding 13-3 lead.
The visiting scrum continued to fall foul of Italian referee Giuseppe Vivarini and Jackson’s simple kick extended the lead further before the half hour mark.
Blues needed a foothold in the game and forced some territory with Copeland again attacking the line while Dafydd Hewitt and Scott Andrews strived to bulldoze past men.
A period of sustained pressure saw Blues come alive with the forwards repeatedly breaking past bodies. Eventually the ball was flung wide left and, despite holding out the initial wave of attack, Ulster were breached as Copeland picked up and brushed off two tackles to go over.
Two minutes later a powerful lineout drive won a penalty and Halfpenny stepped up to reduce the lead to five points at the break as the momentum of the game looked to swing back to Blues.
A miss kick on the restart worked out well for Ulster who went back on the attack with real determination. The ball again went through phase after phase before Olding popped through a gap and fed Marshall on his shoulder, who just made it over the line after TMO consultation.
Ulster suddenly had their tail up chasing the bonus point and turned down a kickable penalty, for not releasing, to kick to the corner. The visiting comeback bid was made even harder when Copeland was sin binned for playing the ball on the floor.
Blues, though, showed real character to take the fight back to Ulster as they twice kicked to the corner after showing forward power at the lineout and a controlled driving game.
The visitors then drove in field and then flowed back left, with Navidi flicking a pass to Smith who dived in the corner for a smart finish. Halfpenny added a sublime conversion from the touchline to cut the lead back to 24-18.
A long range penalty from Pienaar looked to ease home nerves, but again back came fired-up Blues with a penalty allowing Halfpenny to eat into the lead.
Pienaar saw a long range penalty from the halfway hit the left upright and then just minutes later, after obstruction on a high bomb kick, drifted another easier attempt left of the target.
A superb kick into the corner by Olding put Blues under massive pressure as the home side looked to turn the screw as the game entered the final 15 minutes. The decisive bonus point try duly came as the hosts injected pace down the right and Trimble touched down.
The home side looked to rack up the points in the closing minutes, but it was when Blues looked to break from deep that they were undone with a final well worked try from Tuohy.
Timeline:
08m Jackson p 3-0
10m Halfpenny p 3-3
14m Tuohy t 8-3
22m Payne t 13-3
27m Jackson p 16-3
33m Copeland t 16-8
37m Halfpenny p 16-11
41m Marshall t 21-11
45m Jackson p 24-11
50m Smith t Halfpenny c 24-18
53m Pienaar p 27-18
56m Halfpenny p 27-21
66m Trimble t 32-21
80m Tuohy t Pienaar c 39-21
Cardiff Blues: 15 Leigh Halfpenny, 14 Richard Smith, 13 Cory Allen, 12 Dafydd Hewitt, 11 Harry Robinson (Czekaj 77), 10 Rhys Patchell (Davies 74), 9 Lloyd Williams (Jones 67); 1 Gethin Jenkins (Hobbs 58), 2 Marc Breeze (Dacey 67), 3 Scott Andrews (Filise 31), 4 Bradley Davies, 5 Filo Paulo (Reed 56), 6 Josh Navidi, 7 Sam Warburton (Watts-Jones 77), 8 Robin Copeland.
Replacements: 16 Kristian Dacey, 17 Sam Hobbs, 18 Taufa’ao Filise, 19 Lou Reed, 20 Rory Watts-Jones, 21 Lewis Jones, 22 Gareth Davies, 23 Chriz Czekaj
Ulster Rugby: 15 Stuart Olding, 14 Andrew Trimble, 13 Jared Payne, 12 Luke Marshall, 11 Tommy Bowe, 10 Paddy Jackson, 9 Ruan Pienaar; 1 Callum Black, 2 Rory Best (Herring 20), 3 John Afoa, 4 Johann Muller, 5 Dan Tuohy, 6 Robbie Diack, 7 Chris Henry, 8 Roger Wilson
Replacements: 16 Rob Herring, 17 Tom Court, 18 Ricky Lutton, 19 Lewis Stevenson, 20 Mike McCormish, 21 Paul Marshall, 22 Darren Cave, 23 Michael Allen