Mix butter and sugar; add egg, vanilla in a bowl, set aside. Mix flour, baking soda, cinnamon, nutmeg and salt.
Add apples and walnuts to dry ingredients. Fold in liquid ingredients.
Pour into ungreased bundt pan.
Bake for 30-40 minutes at 350ºF.
Cool at least 15 minutes before removing from pan.
Mix caramel sauce ingredients and bring to a boil then serve over cake