Sift flour, baking powder and salt together.
Cream butter and sugar until lightly and fluffy. Add the egg yolks and beat well. Add milk and dry ingredients alternately and beat. Add vanilla.
Beat egg whites until stiff but not dry and fold in gently.
Turn the batter into 3 greased and lightly floured 9" layer-cake pans. Bake 30 to 40 minutes in a preheated 375° oven, then remove from tins and let cool. (Cut the 3 layers in halves to make 6 if you prefer.)
The filling for 3 layers is as follows:
Mix cornstarch and sugar. Add to the crushed pineapple.
Cool until smooth and thickened. Add the orange juice and blend. Spread between the layers and frost as follows:
Put all ingredients, except extract, in to top of a double boiler and cook over hot water, beating continually, from 7 to 8 minutes, or until thick. Add flavoring, and spread around the sides and over the top of the cake.