Step 1: Preheat oven to 325°F and grease a 10-inch Bundt pan thoroughly with butter and flour.
Step 2: Cream the softened butter and granulated sugar together in a large mixer bowl for 5-7 minutes until very light and fluffy.
Step 3: Add eggs one at a time, beating well after each addition to maintain the structure.
Step 4: Whisk together the flour, salt, and baking soda in a separate bowl.
Step 5: Alternately add the flour mixture and the coconut milk to the butter mixture, beginning and ending with the flour.
Step 6: Stir in the rum extract and vanilla extract until just combined.
Step 7: Gently fold in the drained crushed pineapple and the shredded coconut by hand using a spatula.
Step 8: Pour the batter into the prepared pan and bake for 65-75 minutes until a toothpick comes out clean.
Step 9: Cool in the pan for 15 minutes before transferring to a wire rack to cool completely.