2 c. sifted all purpose flour
1 tsp. baking powder
1 tsp. baking soda
1/4 tsp. salt
3 egg whites, room temperature
3 egg yolks, room temperature
1 c. butter, room temperature
1 c. very fine granulated sugar
1 tbsp. grated orange peel
1/2 c. coarsely chopped walnuts and/or 1/2 c. chocolate chips
1 c. sour cream
1/2 c. sugar
2/3 c. fresh orange juice

Heat oven to 325 degrees. Generously grease a 9" bundt or tube pan with unsalted shortening and flour liberally. Make sure all indentations are greased and floured completely. Tap pan gently over sink to remove excess flour.

Sift together flour, baking powder, baking soda and salt. In small bowl of electric mixer beat egg whites until stiff but not dry; set aside.

In large bowl of mixer beat butter and 1 cup very fine sugar at medium speed until blended and fluffy. Add egg yolks. Scrape bowl often with rubber spatula. Stir in orange peel, walnuts and chocolate chips. Add 1/3 dry ingredients and sour cream to butter mixture. Blend well at medium speed. Continue to add dry ingredients while beating and scraping sides of bowl often.

Fold in beaten egg whites. Pour batter into prepared pan. Bake 1 hour or until top springs back when lightly touched. Remove cake from oven. Cool on wire rack 10 minutes.