Combine flour, baking powder, salt, and sugar in sifter.
Stir shortening just to soften.
Sift in dry ingredients.
Add milk and extract and mix until all flour is dampened.
Then beat 2 minutes at a low speed of electric mixer or 300 vigorous strokes by hand.
Add eggs and egg yolk and beat 1 minute longer in mixer or 150 strokes by hand.
Pour batter into a 9-inch tube pan which has been greased and lightly floured on bottom, sides, and tube.
Bake in moderate oven (375°F.) 50 to 55 minutes, or until done.
Cool in pan about 15 minutes.
Then remove from pan and cool right side up on rack.
Sprinkle with confectioners' sugar or frost with Orange or Lemon Butter Cream Frosting