Ingredients

1 batch Italian Meringue Buttercream, vanilla variation, ready to use
Filling:
½ cup sugar
3 tablespoons cornstarch
¼ teaspoon salt
1, 20-ounce can crushed pineapple in juice
2 tablespoon unsalted butter
Cake:
2¾ cups sifted cake flour
1 tablespoon plus ¼ teaspoon baking powder
½ teaspoon salt
5 large egg whites, at room temperature
1¼ cups 100% unsweetened coconut milk (not sweetened cream of coconut)
13 tablespoons (1 stick plus 5 tablespoons) unsalted butter, room temperature, cut into pieces
1¼ cups sugar
1½ teaspoons vanilla extract
Italian meringue buttercream, vanilla variation
3 cups sweetened long-shred coconut

Instructions:

For the Filling: Place sugar, cornstarch and salt in a saucepan and whisk to combine. Drizzle a little bit of the juice from the pineapple over the dry mixture and whisk until smooth. Add remaining pineapple and juice. Bring to a boil over medium heat and cook for a couple of minutes, whisking occasionally until thickened and translucent. Whisk in the butter and cool completely. Refrigerate until chilled and firmed or in an airtight container for up to 3 days, if desired.
For the Cake: Preheat oven to 350˚ F. Coat the insides of two 8-inch by 2-inch round cake pans with nonstick spray, line bottoms with parchment rounds, then spray parchment.
Whisk together flour, baking powder and salt in a medium bowl to combine and aerate; set aside. Whisk together the egg whites and milk in a small bowl; set aside.
In a large bowl with an electric mixer on medium-high speed, beat butter until creamy, about 2 minutes. Add the sugar gradually and beat until very light and fluffy, about 3 minutes, scraping down the bowl once or twice. Beat in vanilla.
Add the flour mixture in four additions, alternating with the egg white/milk mixture. Begin and end with the flour mixture and beat briefly until smooth. Divide batter evenly in pans and smooth tops with offset spatula.
Bake for about 30 to 35 minutes or until a toothpick shows a few moist crumbs. The cake will be tinged with light golden brown around the edges and the top and will have begun to come away from the sides of the pan.
Cool pans on racks for about 10 minutes. Unmold, peel off parchment, and place directly on racks to cool completely. Layers are ready to fill and frost. Alternatively, place on layers on cardboards and double wrap in plastic wrap; store at room temperature if assembling within 24 hours.
For the Assembly: Make sure buttercream is ready to go. It should be very soft - almost like mayonnaise. Place bottom layer on an 8-inch cardboard round (it will make covering it with coconut that much easier later on). Fill the cake with the pineapple filling (you might not need all of it, extra is great over ice cream). Frost the cake’s top and sides with the buttercream. Don't worry if your application job isn’t perfect - you will be covering the whole cake with coconut! See how imperfect it looks when you are still in the midst of it all?
Make sure you have a nice thick layer of buttercream all over (you might still have some leftover, which can be frozen).
Place coconut in a large bowl. Pick up cake (this is where that cardboard round comes in) and hold over bowl. Scoop up coconut with other hand and press generously all over top and sides of cake. Cake is ready to serve. May be refrigerated up to 2 days covered with a cake dome. Make sure to serve at room temperature.