Prepare Vanilla Sugar.
Cream together 1 cup Vanilla Sugar and the butter or margarine; add vanilla.
Sift together cake flour, baking powder, salt, and soda.
Add to creamed mixture alternately with sour cream, beating just till mixed.
Fold in beaten egg whites.
Turn into 2 greased and lightly floured 8x1 1/2-inch round baking pans.
Bake at 350° till wooden pick inserted in center comes out clean, 30 to 35 minutes.
Cool on wire racks for 10 minutes.
Remove from pans; cool thoroughly.
Fill and frost with Fluffy White Frosting.
Sprinkle top and sides with tinted coconut.
Vanilla Sugar: Split 1 or 2 vanilla beans in half lengthwise; place in covered canister with 3 to 5 pounds sugar.
Let age at least two weeks.
Fluffy White Frosting: In saucepan combine 1 cup sugar, 1/3 cup water, 1/4 teaspoon cream of tartar, and dash salt.
Bring to boiling, stirring till sugar dissolves.
Very slowly add sugar mixture to 2 unbeaten egg whites in mixer bowl, beating constantly with electric mixer till stiff peaks form, about 7 minutes.
Beat in 1 teaspoon vanilla.