I also went to Cardiff on Friday visiting a friend at uni, I've only ever been when it's been lovely weather so I always have a great impression of the place, I love it!.
We went to La Tasca the next day. I've never been, or even had tapas before. I'ts great if you're indecisive because you can choose more than more dish as they are quite small dishes. I had chicken croquettes with an amazing garlic sauce, vegetable paella and a ham & pear salad. It was the perfect hangover cur. Need to find a cheap deal for it (let me know if any of you guys have seen one recently!)