2 (6 ounce) cans solid white tuna in water, drained
1/4 cup mayonnaise
1/4 cup finely chopped celery
1 1/2 tablespoons finely chopped onion
1 tablespoon chopped parsley
3/4 teaspoon red wine vinegar
1 pinch salt
1 pinch freshly ground black pepper
4 slices seedless rye bread
8 slices ripe tomato
8 slices Swiss cheese
paprika, for garnish