Combine tuna, carrots, celery, red onion, mayonnaise, red wine vinegar, salt, and pepper in a bowl. Mix well.

Heat a large skillet or griddle over low heat.

Spray the skillet with olive oil. Place two slices of bread on the skillet.

Top each slice of bread with cheese, then the tuna mixture, and a slice of tomato. Cover the skillet and cook on low heat until the cheese is melted and the bread is toasted. Serve immediately.