Preheat oven to 350 degrees. Butter 2 9-inch round pans and line the bottoms with parchment. Then butter parchment and flour pans. Cream butter and sugar, add eggs and beat well. Add apples and nuts. Sift dry ingredients and add alternately with applesauce to butter and sugar, starting and ending with the flour mixture. Pour into prepared pans and bake for 30 minutes or until done. (Toothpick inserted comes out clean.) Invert onto a cooling rack immediately and remove parchment paper. Let cool completely before frosting. To make the frosting, cream together the butter and brown sugar. Add salt, vanilla and milk. Mix well. Slowly add powdered sugar and mix until fluffy.