Tuna sandwich is made from cooked tuna or canned tuna and is almost every time served with a layer of mayonnaise. Served as a light lunch or a snack depending upon the number of ingredients in the filling, tuna fish sandwiches are generally made from white or brown bead. The cooked tuna may be curried, fried and seasoned with salt, pepper and olive oil. The sandwich can be made more filling with the addition of eggs, salad greens like lettuce, celery, green onions and olives. A little mustard sauce goes great with this delicious sandwich.