Beat egg whites and cream of tartar on high speed until whites form stiff peaks. Set aside.
In another bowl, combine remaining ingredients, and beat on low speed for 1 minute. Scrape sides of bowl and beat at medium speed for another 2 minutes.
Fold in egg whites and mix until just combined.
Pour batter into ungreased 10-inch tube pan, and bake at 325ºF for 45-50 min. or until golden brown and top of cake springs back to touch.
Remove from oven and turn upside down to cool 1 hour. Remove from pan.
For frosting, beat together ingredients for 1 minutes, then spread over cake.