Sift flour once, measure, sift 4 more times. Beat egg whites in
large patter until foamy. Add salt and cream of tartar, and
continue beating until they hold up in peaks. Fold in 1/2 cup
flour and vanilla to the other. Fold in egg yolks, 2/3 cup flour,
and 1/2 teaspoon orange extract. Put by teaspoons into
ungreased angel food pan, alternating yellow and white
mixtures. Bake in slow oven (325ºF) 60 to 70 minutes. Invert
pan until cake is cold, then remove.