In a large bowl, cream the butter. Add the sugar and beat until fluffy. Add the egg and beat until well blended. Mix in the soda, salt, cinnamon and nutmeg. Add the flour and stir just until blended. Stir in the apples and nuts. Pour into an oiled 9" round cake pan and bake in a preheated 350 degree oven for 30 minutes until the top springs back when touched lightly with your finger. Serve with Hot Caramel Sauce. In a saucepan, melt the butter, brown sugar and salt. Bring to a boil. Remove from heat and whisk in vanilla and milk. Serve warm sauce over cake.