Taken from the King Arthur flour website, I made the chocolate version for my boyfriend's birthday and everyone loved it. To make the chocolate version, replace 1/4 cup of flour with 1/3-1/2 cup of dutch process cocoa.
Separate the eggs carefully; even a small mount of yolk in the whites will prevent them from beating up properly.
In a large mixing bowl, beat the egg whites with the cream of tartar until foamy. Gradually add 1/2 cup of sugar and contine beating until stiff and glossy. Set aside.
Whisk together the remaining 1 cup sugar with the flour, baking powder and salt. In a separate bowl, beat the oil, milk, egg yolks and flavorings until pale yellow. Add the dry ingredients and beat until well blended, about 2 minutes at medium speed using a mixer, or longer by hand.
Gently fold in the whipped egg whites, using a wire whip or cake blender. Be sure to scrap the bottom of the bowl so the batter is well-blended.
Pour the batter into an ungreased 10-inch tube pan or angel food pan, or two 9-inch round ungreased cake pans.
Bake the cake in a preheated 325 degree oven. If it's in a tube or angel food pan, bake it for 50 minutes, then turn up the heat to 350 for the final 10 minutes, making a total baking time of 1 hour. If you're using two 9-inch pans, bake for about 40 minutes at 325, then 10 minutes more at 350.
NOTE: Don't open the oven during the first 45 minutes of baking; the cake will rise high above the pan, then settle back almost even.
It's done when a finger gently pressed in the middle doesn't leave a print, and you can hear a crackling sound if you listen carefully.
Cool the cake upside down for 1/2 hour before removing it from the pan.
If you've used a tube pan, set it atop a thin-necked bottle, theading the bottle neck through the hole in the tube.
NOTE: Dip a serrated knife in hot water between each slive if you want smooth, even pieces.