• Preheat oven to 350°F. Grease 3 9-inch round cake pans and line with parchment. Grease again and dust with flour.
• Beat the butter until creamy, then gradually add sugar and beat until fluffy. Add eggs one at a time, beating well after each addition.
• Combine the flours and add in four parts, alternating with the milk and the vanilla, Divide the batter among the cake pans (15 oz in each pan).
• Bake for 25-30 minutes or until a cake tester inserted into center of cake comes out clean. Let cakes cool in pans for 10 minutes. Remove from pans and cool completely on wire rack.

Filling

• In a saucepan, whisk the milk, sugar and flour until thoroughly combined. Turn heat to medium-high and cook and whisk constantly over medium-high heat (about 5 minutes) until thickened and bubbly. Remove from heat and add the coconut. Stir in the vanilla extract. Cover and cool to room temperature.
• Spread filling between the two layers of cake. Prepare frosting.

Frosting

• In a stand mixer bowl, combine the egg whites and the vanilla extract and set aside.
• In a medium-size saucepan over high heat, combine the water with the sugar and the cream of tartar. As mixture begins to bubble at edges, stir once to make sure the sugar is dissolved completely, then let come to a rolling boil (about 2 to 3 minutes) and remove immediately from heat. Note: It helps to use a thermometer. If you have a thermometer, insert it. Start whipping the eggs when the temperature reaches 230F, and pull from heat at 240F.
• Begin beating the egg whites with the whisk attachment. Beat until foamy (about 1 minute).
• Without turning off mixer, pour the sugar syrup into the beaten egg whites in a thin, steady stream. Continue beating constantly, increasing speed to medium-high, for about 5 minutes or until stiff peaks form but frosting is still creamy. Beat in the vanilla. Frost top and sides of cake immediately. Generously sprinkle top with shredded coconut.