- Cook the potatoes in boiling water until soft. Drain, keep warm and set aside.
- While the potatoes are cooking, cover the tomatoes in boiling water for 1 minute, then slip out of their skins. Quarter, discard the seeds and chop the flesh.
- In a bowl, combine the tomato flesh with the capers, olive oil, and half the lemon zest and juice. Season with salt and pepper. Add the torn basil.
- Heat the butter in a frying pan. Fry the plaice for a couple of minutes on each side over a medium heat. Squeeze over the remaining lemon juice and zest, and season. Remove from the heat.
- Serve the plaice with the cooking juices poured over the top, together with the tomato mixture and new potatoes.