In a small bowl, combine rum, coconut milk, pineapple juice, and vanilla. Set aside.
In a medium-sized bowl, whisk together the flour, baking soda, and salt. Set aside.
In a large mixing bowl, beat butter and sugar until light and fluffy.
Add eggs to the sugar mixture one at a time, beating well after each addition.
Alternately add the flour mixture and the rum mixture, beating well after each addition.
Fold in the coconut and pineapple.
Fill cupcake liners 3/4 full.
Bake at 350 F for 25 minutes or until cupcakes bounce back when lightly touched.
Cream Cheese Frosting Instructions
Mix cream cheese and butter until light and fluffy.
Mix in powdered sugar a little bit at a time.
Mix in coconut rum.
Pipe or spread on cooled cupcakes.
Note that the original published frosting recipe called for 3 tablespoons of coconut cream instead of the coconut rum. Many people love that version, so I'm leaving it here for reference.If you want to play up the rum flavor in the frosting, you can add a second tablespoon of rum. However, this will make the frosting a little looser and it won't hold up as well. You can use rum extract to avoid this. You can also replace the rum in the frosting with 1 teaspoon of rum extract for a non-alcoholic alternative.Store the cupcakes in the the refrigerator and bring to room temperature before serving.