Soak the onion in cold water with the splash of vinegar for 20 minutes or so. At the same time, soak the semi-dried tomatoes in warm water to plump them up.
Drain the tomatoes and chop them into quite large, long pieces. Put them in a bowl with the olive oil. Drain the onion and add to the bowl, along with the anchovies, parsley, rosemary and a few grinds of black pepper. Grill the brea