1. Preheat oven to 350°F (176°C) and prepare a cupcake pan with cupcake liners.
2. In a large mixing bowl, cream butter and sugar together until light in color and fluffy, about 3-4 minutes. Do not skimp on the amount of creaming time.
3. Add sour cream and mix until well combined.
4. Add egg whites in two batches, mixing until well combined after each. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
5. Combine dry ingredients in a separate bowl. Add half of the dry ingredients to the batter and mix until well combined. Add the pineapple juice and mix until well combined. Add remaining dry ingredients and mix until well combined.
6. Stir in the crushed pineapple and scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
7. Fill cupcake liners about halfway. Bake for 15-17 minutes, or until a toothpick inserted comes out with a few crumbs.
8. Remove cupcakes from oven and allow to cool for 2-3 minutes, then remove to cooling rack to finish cooling.
9. While the cupcakes are cooling, make the frosting. Beat the butter and shortening together until smooth.
10. Add about half of the powdered sugar and mix until smooth.
11. Add the coconut extract, pineapple juice and coconut rum and mix until smooth.
12. Add the remaining powdered sugar and mix until smooth.
13. Pipe the frosting on top of the cupcakes with a swirl. I used Ateco tip 808, a large round icing tip.
14. To decorate the cupcakes, lightly press the coconut flakes onto the sides of the cupcakes then top them with a piece of pineapple and a cherry.

*For the pineapple juice in the cupcakes and frosting, I used the juice from the cans of crushed and sliced pineapple used in the cupcakes and in the frosting. I used an 8 oz can of crushed pineapple (for the cupcakes) and an 8 oz can of sliced pineapple (for the frosting and topping)