Preheat oven to 325°F (165°C). Grease and flour a Bundt pan.
In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
In a large bowl, cream together butter, shortening, and sugar until light and fluffy.
Add eggs one at a time, beating well after each addition.
Mix in the flour mixture alternately with the milk, beginning and ending with the flour mixture.
Stir in vanilla, lemon, rum, butter, and coconut extracts.
Pour batter into prepared Bundt pan.
Bake in preheated oven for 90 minutes, or until a toothpick inserted into the center of the cake comes out clean.
Allow cake to cool in pan for 10 minutes, then turn out onto a wire rack to cool completely.