Preheat the oven to the lowest heat setting. Slice the tomatoes in half horizontally and scoop out most of the seeds. Salt the insides and turn cut side down on a wire cake tray - leave for half an hour, then rinse and dry.
Mix the crushed garlic with the oregano and black pepper. Spread this mix over the cut side of the tomatoes. Place the tomatoes cut side up in a roasting tray and dribble over olive oil into the tray. Cook in a low oven at 100C/200F/Gas 1 for three hours or leave in the sun for up to two days, taking them in at night.
Place the tomatoes in a sterilized kilner jar and cover with extra virgin oil. Use in any recipe that requires sun-dried tomatoes.