- 1 (6 ounce) can water-packed tuna, drained and flaked
- 1/4 cup finely chopped celery
- 1/4 cup finely chopped onion
- 1/4 cup mayonnaise
- 4 hamburger buns, split
- 4 slices mozzarella cheese
- 4 tomato slices
- 4 lettuce leaves
- In a small bowl, combine the tuna, celery, onion and mayonnaise. Spread on bottom of buns; set bun tops aside. Top tuna mixture with a slice of cheese and tomato. Place on an ungreased baking sheet. Bake, uncovered, at 350 degrees F for 12-15 minutes or until heated through and cheese is melted. Top each with a lettuce leaf; replace bun tops.