Chop the tomatoes in roughly the same size as the bread, toss with a little olive oil and set aside to release all their juices.
Slice the onion thinly and toss with the coarse sea salt; set aside for about 15′.
Half the peppers, remove the seeds and slice thinly. Rinse the onion with plenty of fresh water and drain thoroughly.
Place the bread in a large serving bowl; top with the chopped tomatoes and all their juices, the onion, and sliced peppers. Add the olive oil, vinegar, sea salt flakes and harissa spice and toss to combine. Serve with torn basil leaves on its own, or alongside a nice piece of grilled fish or meat.