Preheat the oven to 350°F/177ºC. Prepare three 6-inch (15cm) or two 8-inch (20cm) cake pans by spraying the sides with cooking spray and fitting a parchment paper circle to the bottom of the pan.

Add the sifted cake flour, baking powder, baking soda, and salt into a medium bowl and whisk to combine. Set aside.

In the bowl of your stand mixer fitted with the paddle attachment, beat the butter on high for two minutes until it’s light and creamy. Add the sugar and continue to mix on medium-high for another two minutes, scraping down the bowl and paddle as needed.

Turn the mixer to low speed and add the egg whites one at a time, mixing until well combined. Add the sour cream, vanilla extract, and coconut extract and mix for one minute on high. Scrape down the bowl and paddle once more.

Turn the mixer to low, add in the dry ingredients all at once. When they’re just beginning to combine, add the canned coconut milk in a slow, steady stream. Continue to mix on low until incorporated. Scrape the sides and bottom of the bowl and give it a few stirs by hand to make sure there are no large lumps, then gently fold in the shredded coconut.

Pour the batter evenly into the prepared cake pans and bake for 35-40 minutes. They’re done when they spring back to the touch and a toothpick inserted into the middle comes out clean. Let the cakes cool in the pan for five minutes before turning them out onto a wire rack for an additional few hours of cooling.

Sift together the powdered sugar and cornstarch (if using) and set aside. In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and cream cheese on medium-high until light, fluffy, and uniform (no lumps), about 5 minutes.

Turn the mixer to low speed and add the powdered sugar and cornstarch mixture a few cups at a time, mixing thoroughly after each addition and scraping down the bowl and paddle as needed. Add the vanilla extract, coconut extract, coconut milk, and salt and mix on low for another minute, until fully combined and smooth.

Once the coconut cakes are completely cooled, level them to your desired height. Add a swipe of coconut cream cheese buttercream onto a cardboard cake circle and place the first cake layer on top. Fill and stack the cake layers with coconut cream cheese buttercream, then crumb coat the cake with a thin layer of coconut cream cheese buttercream.

Place the crumb coated cake in the refrigerator for at least 30 minutes to let the frosting firm up. To create the look pictured, frost a smooth buttercream finish with coconut cream cheese buttercream.

Place the cake back into the refrigerator for about 15 minutes, until the frosting is slightly set but still tacky, then gently press the shredded coconut onto the sides and top of the cake.

Once the sides and top of the cake are covered in coconut, place the remaining coconut cream cheese buttercream into a piping bag fitted with Wilton Tip 4B. Pipe a swirl border on top of the cake and finish with pastel rainbow candles if desired.