Grease a large baking dish. Saute onion in butter. Add soups, sour cream and tomatoes. Stir to mix. Bring broth to a boil and keep hot. Dip tortillas one at a time in broth to soften. Put on plate. In each tortilla place a serving of chicken,2 tablespoons of soup mixture and 2 tablespoons of cheese. Roll and place seam side down in dish. Pour remaining soup and cheese on top. Cover with foil and bake for 30 minutes at 325.