Prehead oven to 350º. One ungreased 10 inch tube pan (angle food pan).
In a large mixing bowl, beat egg whites with cream of tartar or lemon juice until foamy. Gradually add 1/2 cup sugar and continue beating until very stiff. Set aside
Whisk together the remaining 1 cup suar with flour, baking powder and salt
In a separate bowl, beat the oil, milk and egg yolks and vanilla until pale yellow
Add dry ingredients and beat until well blended, about 2 minutes at medium speed.
Gentley fold in the whipped egg whites, using a wire whip.
Be sure to scrap the bottom of the bowl so the batter is well-blended. Pour batter into pan.
Bake about 55-60 minutes.
Coo lcake upside down for 1/2 hour before removing from pan. To cool set pan atop a thin-necked bottle. So hole sits on neck of bottle.
After 30 minutes use thin-bladed flexible spatula to free cake from from sides and tube of pan. Finish cooling.
Cake wrapped well will keep for 2 days at room temperature and frozen for 3 months and 5 days in fridge.
Serve with fresh fruit or frost with a glaze