Preheat oven to 350.
Heavily grease a bundt pan.
In a large bowl, cream together butter and sugar.
Beat in eggs, one at a time.
Add vanilla, flour, baking soda, cinnamon and salt.
Beat until blended
Stir in apples.
Pour batter into prepared pan.
Bake 45-50 minutes or until toothpick inserted in center comes out clean.
Cool in pan for about 10 minutes before turning out onto plate.
In a small saucepan combine butter, brown sugar and milk.
Cook over medium heat, whisking constantly, until mixture boils.
Immediately remove from heat and allow to cool for about 10 minutes.
Add vanilla and powdered sugar and whisk until blended.
Pour over cake, allowing it to run down the sides.