Preheat oven to 375 degrees F (190 degrees C). Line the bottom of two 9 inch round pans, two 9 inch square pans, or one 10 x 16 inch pan.
Combine sifted flour, baking powder, and salt; sift together three times.
Beat egg whites until foamy. Add 1/2 cup of the sugar gradually, and continue beating only until meringue will hold up in soft peaks.
Cream shortening. Add remaining 1-1/4 cups sugar gradually, and cream together until light and fluffy. Add flour alternately with milk, a small amount at a time; beat after each addition until smooth. Stir in vanilla. Add meringue, and beat thoroughly into batter. Spoon the batter into the prepared pan or pans.
Bake cake in 9 inch round pans or 10 x 16 inch pan for about 30 minutes. The baking time for the square pans is 25 minutes. Cool. Spread Lemon Orange Filling between layers, and Snowy Boiled Icing over top and sides of cake. Decorate plate with small flowers.
