Preheat the oven to 350 degrees Fahrenheit. Spray a 13 x 9 x 2-inch pan with non-stick cooking spray and set aside.: When the oven warms to 350 degrees Fahrenheit , you should feel a steady, warm air when you briefly open the door; this even heat is essential for a uniform rise and golden edges. Spraying the pan prevents sticking and encourages clean slices, which matters when you want neat servings. A common trap is rushing the oven warm up, which can produce uneven texture and cause the center to cook slower than the edges, so always wait until the oven reaches temperature.
In a large bowl, add 1 (13.25-ounce) box yellow cake mix, 1 (8-ounce) can crushed pineapple, 1/2 cup vegetable oil, and 4 large eggs. Using an electric hand mixer on medium speed, mix for 2 minutes.: As you mix, you will hear a consistent, humming beat from the mixer and see the batter turn smooth and glossy, with small air bubbles forming that promise a tender crumb. The vegetable oil lends silkiness while the eggs build the batter's structure, and the crushed pineapple disperses tiny pockets of fruit. Avoid overmixing beyond the recommended time, because that can produce a tougher texture as gluten develops; stop when the batter looks homogenous and slightly aerated.
Pour the batter into the prepared pan and bake for 25-30 minutes, or until a toothpick comes out clean from the center.: During baking you will notice the cake edges pulling away slightly from the pan and the top turning a warm golden hue, a great visual cue the center is nearly done. The toothpick test is the most reliable check, and when it emerges clean or with a few moist crumbs, the cake is ready. Be careful not to open the oven too often, which can make the cake sink, and avoid overbaking since that dries the crumb and reduces the cake's ability to absorb the soaking liquid.
In a small bowl, whisk together 1 cup cream of coconut and 1/2 cup pineapple juice.: Whisking these creates a glossy, pourable mixture where the sweetness of the cream of coconut integrates with the bright, tangy pineapple juice . The combined aroma is intensely coconut and pineapple, and the liquid should be smooth with no lumps. If the mixture seems separated, a brief, vigorous whisk will bring it back together; do not heat it, because warming changes the texture and reduces its ability to soak into the cake properly.
When the cake is done baking and is still warm, use a large fork to poke holes all over the cake. Pour the coconut and pineapple mixture evenly over the cake and allow it to be completely absorbed and fill the poked holes.: As you poke, the surface will give slightly and steam may rise, releasing the scent of baked yellow cake . Pouring the coconut pineapple liquid while the cake is warm helps it sink into the crumb and fill those little wells, creating pockets of moist, flavored cake. Pour slowly and allow time for absorption between pours so the top does not pool; the most common mistake is pouring too fast and ending up with uneven soaking or a soggy surface rather than evenly infused cake.
In the bowl of a stand mixer, add 1 1/2 cup heavy cream and 1/4 cup cream of coconut. Using the whisk attachment, whip until medium stiff peaks form, about 5 minutes.: As you whip, the sound changes from liquid sloshing to a thicker, rhythmic whipping, and the cream will begin to leave trails and hold shape on the whisk. Achieving medium stiff peaks means the whipped cream stands tall but is still slightly glossy, perfect for spreading. Watch closely to avoid whipping past this stage into butter; if you see graininess, you have gone too far and should start again with a fresh bowl and chilled cream.
Once the cake is completely cool, spread the whipped cream over the top. Top with 1/2 cup toasted sweetened shredded coconut. Refrigerate until ready to serve.: Spreading the whipped topping on a fully cooled cake prevents it from sliding off, and you will feel the cool, pillowy texture contrast with the denser cake below. The toasted sweetened shredded coconut adds crispness and a toasty scent that balances the sweet cream, and a final chill helps the layers set so you can slice clean pieces. A common error is refrigerating before the soak has settled fully, which can lead to uneven texture; always ensure the soak is absorbed and the cake has cooled before topping and chilling.