Cook large shells by package directions and drain.  In the mean time, Mix together 1 can of drained tuna, 1 sm box of cooked frozen chopped brocolli (drained) , 1 half can of any cream soup, (cream of celery is the best)  about 1 cup of shredded cheddar cheese and some chopped tomatoes.  Sprinkle with 1 tsp lemon juice.   When the shells are ready stuff them with the mixture and place in buttered baking dish in single layer.  This next step is very important to make sure the shells stay soft while baking.  Brush the shells with melted butter.   Bake in 350 oven about 20 minutes then sprinkle with more cheddar cheese. Bake 10 more minutes