The New Zealand full-back was named in Graham Henry's first Wales squad and could not have chosen a better opportunity to rubber stamp his credentials - after all, Mike Rayer, his chief rival for the No 15 shirt, was on the opposing side.
Howarth scored two tries, three conversions and a penalty and Cardiff were unable to counter, going down 34-25 despite two tries from Liam Botham.
Another Welsh international full-back, Swansea's Matthew Back, is likely to be out of action for six weeks after dislocating his left elbow in the 27-16 win over Gloucester at St Helens.
Back scored the first of Swansea's three tries as they hit back from an early nine-point deficit as the Kiwi outside-half Simon Mannix kicked Gloucester into a well-deserved lead.
The Richmond coach, John Kingston, will give his battle-weary troops two days rest before an arduous two-week programme which will see the team on the road for three successive away games against Wasps, Sale and Leicester. After a spate of injuries, Kingston was finally able to field a full-strength pack and his team responded by beating West Hartlepool 41-23 in the Allied Dunbar Premiership. The Argentinian scrum-half Agustin Pichot, full-back Lee Best and Welsh back-rower Scott Quinnell scored two tries each with Nick Walne grabbing the other.
"I've finally got a fit pack and now all the backs are going down like flies. It just doesn't seem fair," Kingston said. The West Hartlepool director of rugby, Mike Brewer, must consider Kingston's troubles little more than an irritant compared to his more chronic problems. Earlier in the week, he threatened several players with the sack unless results improved and this performance, their fifth successive defeat, will do little to aid the cause of those under threat of the chop.
Ebbw Vale's nightmare European Cup campaign continued yesterday as their total points conceded in just three games passed the 200 mark. The Welsh Cup winners have found the level of competition more like a giant leap than a step up ever since they went down to a record 108-16 defeat to Toulouse in the opening Pool C game.
Yesterday, though, they would have expected to do much better at Eugene Cross Park against an Ulster side who had not exactly been pulling up arboretums. Simon Mason led the rout for Ulster, kicking 26 points as his side romped home 61-28 for their first European win this season. He converted all his side's seven tries and landed all four penalties.
Munster put up a fierce fight before falling to the group favourites Perpignan 41-24 in Pool B. The Irish side scored three tries but found the French just too strong.