Cut ciabatta into large cubes and saute in 3 tablespoons olive oil until crispy and golden brown. Drain on paper towels.
Rinse and halve tomatoes. Rinse and slice scallions into fine rings. Rinse and chop celery. Peel, halve and cut the onion into strips. Peel garlic and finely chop. Peel cucumber, cut in half lengthwise, remove seeds and dice.
Place all prepared vegetables with capers in a bowl. Mix with the remaining oil, vinegar and the lemon juice. Season with salt and pepper and let stand for about 10 minutes. Toss with parsley and bread. Season to taste and serve.