Begin by pre-heating the oven to 325°.
Grease and flour a Bundt pan or funnel pan.
To the bowl of an electric mixer, add the flour, corn starch, baking powder, salt, sugar, butter and oil.
Mix on low speed, for just a couple of minutes, until the butter and oil are well incorporated and the mixture is crumbly and sandy looking.
Mix in the milk and then mix in the eggs, one at a time; scrape the sides and bottom of the bowl well after each egg is added.
Finally, mix in the rum and vanilla extract until the batter is smooth.
Pour the batter into the prepared pan and bake for 55 - 65 minutes or until a wooden toothpick, inserted into the center, comes out clean.
Completely cool the cake on a wire rack.