Preheat oven to 350°. Spray a 9x9-inch square baking dish with nonstick cooking spray; set aside. In a medium bowl, mix together vegetable oil, eggs, and water. Mix with a spoon until well combined. Stir in ¾ cup coconut flakes, ½ cup macadamia nuts, vanilla baking chips, and rum extract. Spread batter in prepared pan. Bake 33 to 36 minutes or until toothpick inserted in center comes out clean.

Meanwhile, place pineapple slices in a 9-inch pie plate; sprinkle with brown sugar. Bake alongside brownies for 20 minutes.

While brownies are still warm, place pineapple slices on top of cooked brownies. Sprinkle with an additional ½ cup macadamia nuts and an additional ¼ cup toasted coconut flakes. Store in the refrigerator for up to 5 days.