1/2 c. diced onion
2 tbsp. butter
2 cans tuna
1/2 c. milk
1/2 c. diced celery
1 1/2 c. cooked rice
1 can mushroom soup
1 cup grated cheese

Saute onion and celery in butter until tender. Add all other ingredients and mix well. Pour into greased casserole, cover with cheese. Bake at 350 degrees for 30 minutes.