Preparation / Directions:
Sift together flour, sugar, baking powder and salt into bowl. Make well in center and add water, oil, egg yolks, grapefruit juice and lemon zest. Beat until very smooth. Beat egg whites with cream of tartar until stiff but not dry. Gradually add egg whites to batter and fold in gently until just blended. Do not stir. Turn batter into ungreased 9-inch springform pan and bake at 350 degrees 30 minutes, or until top of cake springs back when lightly touched. Cool in pan on rack. Loosen edges of cake carefully and remove from pan. With serrated knife, cut cake crosswise to make 2 layers. Fill with part of White Mountain Frosting. Frost top and sides with remaining frosting. Sprinkle generously with coconut.
WHITE MOUNTAIN FROSTING: Combine sugar, water, corn syrup and salt in saucepan. Cook and stir over low heat until sugar dissolves. Cover saucepan 2 to 3 minutes to dissolve sugar crystals on sides of pan. Uncover and continue cooking to soft ball stage (236 degrees on candy thermometer). Remove from heat. Beat egg whites until stiff but not dry. Add hot syrup in slow stream, beating constantly. Blend in vanilla and continue beating until frosting holds deep swirls.