Prep time: 20 minutes, plus 40 minutes baking time. Preheat oven to 350°F. Mix together shortening and sugar. Add egg and apple sauce and mix well. Add flour, salt, cinnamon and nutmeg and mix until well combined. Add baking soda to boiling water (it will foam up!) and then add to cake batter, mixing well. Pour batter into a well greased 9x13 inch pan and bake about 40 minutes, or until toothpick inserted in center comes out clean. Combine milk, brown sugar and butter in a saucepan and bring to a boil. Boil for 3 minutes, then pour over hot cake and let cool before serving.