10 egg whites
1 teaspoon pure lemon or orange extract
1 1/2 cups confectioners' sugar
1 cup all purpose flour
6 egg yolks
1 teaspoon cream of tartar

Preheat oven to 350°F. In the bowl of an electric mixer, beat egg whites until stiff and dry (the egg foam will no longer be shiny), adding sugar gradually while mixing. Stop the mixer occasionally to use a spatula to scrape the unbeaten whites up from the bottom of the bowl.

in a separate bowl, beat the egg yolks until they are thick and lemon colored. Beat in lemon extract.

Whisk flour with cream of tartar until well combined; stir into egg yolks. Cut and fold egg whites into batter.

Bake for 50-60 minutes in an ungreased angel-cake pan, reducing heat to 325°F after 15 minutes.

TIP: Don't open the oven to peek until the cake has been baking for at least 45 minutes - and be quick to close the door or the cake may fall!