Pre-heat the oven to 170C. Cut the stale bread into cubes and toast them for around twenty minutes when they start turning golden.
Take them out and let them cool in a plate. Chop the onion, cucumber and the tomatoes and put them in the salad bowl. Add the bread to the bowl and mix well with the vegetables.
Make the dressing in a small mixing bowl. Whisk together the olive oil, vinegar, capers, sugar and some salt and pepper. Do a taste check for seasoning. Add this dressing to the salad bowl and stir well to combine everything together. Cover it with a cling film and let it refrigerate overnight so that the flavors blend well with each other. The next day, garnish with shredded basil just before serving.