Preheat oven to 325 degrees. Grease and flour an bundt cake pan.
In a large bowl add the flour, baking powder, pudding, cornstarch, and salt and whisk until combined.
Using an electric mixer add sugar and softened butter and cream together until fluffy. Add in eggs, oil, milk, spiced rum and vanilla. Mix just until combined.
Add in the flour mixture and mix on low for 1-2 minutes. Pour into bundt pan.
Bake for 55-60 minutes or until toothpick comes out clean.