Cut the tomatoes in half horizontally. Scoop out the ribs and pulp from each half tomato, taking care to leave the outside shell unbroken. After salting the insides of the tomatoes, drain them upside down on a rack for at least an hour. Chop up the pulp and set in a bowl with its juices.
Meanwhile, make your topping. Place the breadcrumbs in a mixing bowl and add the capers, anchovies, garlic, parsley and/or basil, salt, pepper and a drizzle of olive oil. Mix everything together and moisten to taste with a few spoonfuls of the chopped tomato pulp and its juices. Taste and adjust for seasoning.
When the tomatoes have finished draining, turn them right-side up and fill the insides of each tomato half loosely with the breadcrumb topping. Place them in a well greased baking dish or sheet.
Drizzle the tomatoes generously with olive oil and bake them in a hot (200C/400C) for a good half hour, or until they are golden brown on top.
Serve warm or at room temperature.