Fry cube steak until cooked. Place on paper towels to drain. Save pan drippings. Add soup to drippings and bring to a boil. After steak has cooled a little, cut into bite-size pieces. In a large round casserole dish layer as follows: potato,onion,steak and repeat. Pour soup mixture on top. Bake at 350 degrees for 30 minutes or until bubbly.