I substituted a mix of locally grown heritage tomatoes for plum tomatoes, you can use whatever fresh tomatoes you can find and like. You can also add peeled sliced cucumber and radishes for variety.
Cut the bread into cubes and place in a baking tray. Drizzle with half of the olive oil and sprinkle generously with garlic salt. Place in the oven and bake for fifteen minutes, stirring halfway through. Remove and allow to cool.
Place the shallots in a small bowl and sprinkle with the sugar and vinegar, cover and leave for an hour in the bottom of your fridge.
When the bread is cold place in a mixing bowl. Chop and add the tomatoes, capers and torn basil. Season generously and add the shallot mix and the remaining oil. Mix all together and leave to soak for five to ten minutes before serving.