1 (6 1/2 oz.) can water pack tuna, drained
2 tbsp. chopped onion
1 tsp. prepared mustard
Hamburger buns
2 tbsp. sliced water chestnuts
Safflower mayonnaise to moist
Sliced low fat cheese

Mix tuna, onion, water chestnuts and mustard; moisten with mayonnaise. Warm hamburger buns; spread bottom halves with tuna. Broil 5" from heat about 3 minutes; add cheese. Broil 2 minutes longer or until cheese melts. Lettuce, tomato and sliced onion may be added, if desired. Add bun tops.