Preheat oven to 350 degrees F (180 degrees C).
Prepare the Pineapple. To do this, cut off both ends of the pineapple so that it stands upright. Grab your knife, starting at the top, cut the peel away in one swift downward motion.
Turn the pineapple and continue cutting the rind away in strips. Cut away any brown eyes or sharp brown needles. Quarter the pineapple. Cut the core away at an angle, and finely chop the pineapple.
Grease and flour a mini bundt pan, or if you have two then grease two. It’ll just save you from having to bake the cakes in two batches. Or you can also make cupcakes instead and line a cupcake pan with liners.
Sift together the All-Purpose Flour (2 cup), Baking Powder (1 teaspoon), Baking Soda (3/4 teaspoon), and Salt (1/2 teaspoon) into a bowl.
In the bowl of a mixer fitted with the paddle attachment, add the Unsalted Butter (1/2 cup). Whip for 3 minutes.
Beat in the Brown Sugar (1/4 cup) and Granulated Sugar (3/4 cup). Cream together on medium-high for about 5 minutes, or until mixture is fluffy. Add the Large Egg (2) one at a time, mixing well after each addition.
Scrape down the sides and bottom of the bowl frequently throughout mixing. Add the Dark Rum (2 tablespoon) (or vanilla) and Coconut Extract (1 teaspoon) (if using), and mix once more. Add the Coconut Milk (1 cup) and mix again.
Add the dry ingredients in two batches, mixing just until incorporated after each addition. You want to be careful not to over-mix the cake batter at this point as it can become tough and dry.
Fold in the Pineapple (1/2 cup). Using a medium ice cream scoop, scoop out the batter into the prepared mini bundt pan. Rap the pan on the counter a few times to release any air bubbles lodged in the batter.
Bake for about 20-25 minutes or until golden brown. Rotate the pan halfway through baking to ensure even browning and cooking. You’ll know the cakes are done when a toothpick, inserted in the middle, comes out clean.
Once baked, remove the pan from the oven and allow to cool on a rack for about 20 minutes. Run a knife along the edges of each cake to loosen it. Invert the pan onto a tray or cooling rack; the bundt cakes should come right out.
Clean the pan and repeat with the remaining batter, making sure to grease and flour again as well. Allow the cakes to cool completely before glazing.
To make the glaze, mix the Powdered Confectioners Sugar (1 pound), Rum (1 tablespoon), and whole Milk (3 tablespoon) in a bowl. As you whisk, stream in the Fresh Pineapple Juice (3 tablespoon), a tablespoon at a time. Whisk until the glaze is thick, but still pourable.
Spoon the glaze over each bundt cake, allowing it to drip down onto the sides.
Serve right away or cover and place in the fridge until ready to eat. Store any leftovers covered in the refrigerator. Enjoy!