CAKE:

2 1/2 c. unsifted cake flour
2 1/2 tsp. baking powder
1 tsp. salt
1 c. milk
1/4 c. cold water
1 1/2 tsp. vanilla
4 egg whites, at room temperature
1 1/2 c. sugar
1/2 c. vegetable shortening
1/4 c. (1/2 stick) butter, softened

LEMON FILLING:

2/3 c. sugar
2 tbsp. cornstarch
1/8 tsp. salt
3/4 c. water
1/3 c. strained fresh lemon juice
1 tbsp. butter
3 egg yolks, slightly beaten
1 tbsp. grated lemon rind

FLUFFY WHITE FROSTING:

1 c. sugar
1/8 tsp. cream of tartar
1/8 tsp. salt
2 egg whites
1/4 c. cold water
1 1/2 tsp. vanilla
2 to 3 c. grated fresh or canned coconut

Preheat oven to moderate 350 degrees. Grease and flour three 9-inch round layer cake pans; set aside.

Prepare cake: Sift together cake flour, baking powder and salt onto sheet of wax paper; set aside. Combine milk, water and vanilla in 2-cup glass measure or small bowl; set aside.

Beat egg whites in medium bowl until frothy. Gradually beat in 1/4 cup of the sugar until soft peaks form; set aside.

Combine shortening, butter and remaining sugar in large bowl. Beat on medium- high speed until light, 2 to 3 minutes. Reduce speed to low; beat in dry ingredients alternately with milk mixture, beginning and ending with dry ingredients. Fold in beaten whites, half at a time. Divide batter among prepared pans, spread evenly to edges.

Bake in preheated moderate 350 degree oven for 20 to 25 minutes or until edges start to pull away from sides of pan. Cool cakes in pans on wire racks for 10 minutes. Turn cakes out onto wire racks to cool completely.

Prepare filling: Combine sugar, cornstarch and salt in small saucepan. Stir in water, lemon juice and butter. Cook, stirring, over medium heat until mixture comes to boiling, 3 to 4 minutes. Lower heat; cook 1 minute, stirring constantly. Stir 1/4 cup hot mixture into yolks in small bowl. Quickly stir yolk mixture into saucepan. Cook, stirring, 1 minute. Do not boil.

Remove saucepan from heat. Add lemon rind. Cool 10 minutes, stirring once or twice. Cover; refrigerate until chilled.

Prepare Frosting: Combine sugar, cream of tartar, salt, egg whites and water in top of double boiler. Beat 1 minute. Then beat over simmering water, 5 to 7 minutes or until frosting is thick, shiny and holds firm peaks. Remove from simmering water. Beat a little longer until cool. Beat in vanilla; set aside.

Stir Lemon Filling to soften. Place cake layer on serving plate. Spread with half the filling. Top with second layer. Spread with remaining filling. Top with remaining layer. Frost top and sides with frosting. Sprinkle top and sides with coconut.