Preheat oven to 350 F, spray a large Bundt pan with nonstick cooking spray. Set aside.

In a large mixing bowl - or the bowl of an electric mixer, stir together the flour, sugar, pudding mix, baking powder and salt.

Add the melted butter, pina colada mix, rum, eggs, and vanilla extract to the large bowl of flour mixture.

Whisk on medium speed with an electric mixer for about 2 or 3 minutes - scraping down the sides of the bowl halfway through. The cake batter should be very smooth.

Fold in coconut and pineapple, or mix on low speed until combined.

Pour batter into the prepared pan, smoothing the top.

Bake until golden brown and a butter knife or wooden toothpick inserted into the thickest part of the cake comes out clean – about 1 hr 15 minutes.

Remove from oven and place on cooling rack while making rum soak.

In a small saucepan, combine butter, water and sugar. Carefully bring to a boil over medium heat – do not allow to boil over.

Reduce to a simmer and cook until sugar is dissolved and syrup becomes slightly thicker, about 5 minutes.

Remove from heat and stir in the rum.

While cake is still cooling in the pan, use a fork or the narrow end of a chop stick to poke holes over the surface of the cake.

Fully cool cake - to room temperature - in the pan before turning out onto serving platter.

In a medium bowl, mix icing sugar into the rum to make a thick mix.

Warm it in the microwave for a few second if it gets too firm, then pour over the cake.

If desired - while glaze is still wet - garnish with toasted coconut and/or maraschino cherries.

Leftover cake can be wrapped in plastic wrap and stored at room temperature for a week or so.