tuna fish sandwich recipe

Ingredients: 1 can (5-6 ounces) tuna, drained 1/4 cup mayonnaise 1 tablespoon Dijon mustard (optional, for extra flavor) 1 celery stalk, finely chopped 1/4 red onion, finely chopped 1 tablespoon fresh parsley, chopped (optional) Salt and freshly ground black pepper to taste 4 slices of your favorite bread (white, whole wheat, or rye) Lettuce leaves Tomato slices