Preheat oven to 325 F. Grease a 9 x 13 pan. Cream together butter, salt and sugar. Beat in eggs. Add flour, baking powder, baking soda, cinnamon and mix well. Add apple slices and nuts. Mixture is very thick. Spread evenly in pan and bake for 35-40 minutes. Serve warm alone or with vanilla ice cream/frozen yogurt.