Position a rack in the center of the oven and preheat to broiler. In a bowl, combine the tuna, artichoke hearts, spinach, lemon juice, onion, celery, EVOO, parsley, capers and garlic; season with pepper.
Split the ciabatta rolls and arrange on a baking sheet. Top the bottoms with even mounds of tuna salad and cheese. Broil to melt the cheese and toast the roll tops. Add the sliced tomato to the sandwiches, cover with the roll tops and serve.