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1
In a large bowl, whisk milk, pudding mix and zest 2 minutes. Cover and refrigerate at least 1 hour.
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2
Place egg whites in a large bowl; let stand at room temperature 30 minutes. Preheat oven to 350u00b0. Line bottoms of three greased 9-in. round baking pans with parchment; grease paper.
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3
In a large bowl, cream butter and sugar until light and fluffy. Beat in vanilla. In another bowl, whisk flour, baking soda, baking powder and salt; add to creamed mixture alternately with buttermilk, beating well after each addition. With clean beaters, beat egg whites on high speed until stiff peaks form; gently fold into batter.
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4
Transfer to prepared pans. Bake 25-30 minutes or until a toothpick inserted in center comes out clean. Cool in pans 10 minutes before removing to wire racks; remove paper. Cool completely.
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5
For frosting, in a large heavy saucepan, combine sugar, egg whites, water, salt and cream of tartar over low heat or in a double boiler over simmering water. With a portable mixer, beat on low speed 1 minute. Continue beating on low over low heat until frosting reaches 160u00b0, about 12 minutes.
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6
Pour into the bowl of a heavy-duty stand mixer; add vanilla. Beat on high until frosting forms stiff peaks, about 7 minutes.
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7
Using a long serrated knife, cut each cake horizontally in half. Place one cake layer on a serving plate; spread with 3/4 cup filling to within 1-inch of edge. Repeat four more times. Top with remaining cake layer. Frost top and sides of cake. Sprinkle top with coconut; gently press coconut into frosting on sides of cake. Store in the refrigerator.
