Heat oven to 350 degrees. Grease bundt pan. Sift flour with baking soda.
In a separate bowl, cream oil with sugar until light and smooth. Beat in eggs one at a time, beating well after each addition. Fold in flour mixture. Gently fold in apples and vanilla. Mixture will be thick.
Spoon mixture into prepared pan. Bake until skewer inserted in center of cake comes out clean, about 1 1/4 hours.
Five minutes before cake is done, prepare topping by combining brown sugar, milk, butter and vanilla in a sauce pan. Melt over low heat, stirring constantly until smooth. Boil until topping coats spoon, about 3 minutes, stirring the entire time.
Turn cake out onto rack while still warm. Drizzle topping on cake. Allow to cool, then re-spoon topping that has dripped off the cake. Enjoy!