To make the cake: Preheat oven to 350 Degrees F. Sift the cake flour, baking powder and salt together. Set aside.
In another bowl, combine the milk, egg whites, and vanilla.
In a third bow, cream the softened butter and sugar together until light and fluffy.
Add the flour mixture and the milk mixture alternately to the butter and sugar, beginning and ending with the flour.
Divide the batter evenly between two prepared 9-inch round cake pans.
Bake the cakes for 25-30 minutes until a tooth pick inserted into the cake comes out clean.
Allow the cakes to cool for 5 minutes before transferring from the cake pans to wire cooling racks. Allow the cakes to cool completely.
To make the buttercream frosting: Using an electric mixer, beat the butter and shortening together.
Add in the powdered sugar one cup at a time until combined.
Add in milk and beat until frosting is light and fluffy.
If Necessary, add in additional milk one tablespoon at a time until the desired consistency is reached. Reserve 3/4 cup of the buttercream and combine with 3/4 cup of shredded coconut.
To assemble the cake: Using a sharp, serrated knife, cut each cake in half horizontally so that you have four layers.
Place the first layer of cake on a platter or cake stand.
Spread one cup of lemon curd on the bottom layer, leaving a 1/4 border.
Top with the second layer of cake.
Spread the reserved buttercream and coconut mixture on the second layer, leaving 1/4 border.
Top with the last layer of cake. Transfer to refrigerator for 20 minutes to set up.
After the cake has chilled for 20 minutes, make a crumb coat on the cake by frosting the cake with a small amount of frosting. You should be able to see the crumbs and cake through this thin layer of icing.
Refrigerate the cake for 30 minutes, or until the crumb coat is dry.
After 30 minutes, frost the cake with the remaining coconut so that the cake is completely covered. Store finished cake in the refrigerator until ready to serve.