Preheat oven to 350 degrees F.
Prepare a 10-inch, 12 cup bundt or tube pan with Wilton Cake Release or grease with solid vegetable shortening then flour or sugar. I dust it with granulated sugar after I grease it with Crisco shortening. The sugar doesn't leave white areas in the cake. You can also use two 9x5x3 inch loaf pans.
In a large bowl of an electric mixer, beat egg whites on high speed until foamy. Gradually beat in 1cup sugar, 1/4 cup at a time. Beating after each addition. Continue beating until soft peaks form. Set aside.
Sift flour with baking powder and salt. Set aside.
In another bowl of an electric mixer, beat egg yolks on high speed with remaining sugar, butter, and vanilla (or almond) until light and fluffy. This will take about 5 minutes.
Turn the mixer down to low speed and blend in flour mixture until smooth and well combined.
Still on low speed, gradually beat in the egg whites until just blended. Scrap the sides of the bowl.
Pour the batter into your prepared pan.
Bake at 350 degrees F for 60 to 65 minutes or until a wooden pick inserted in the thickest part comes out clean or with dry crumbs. (My cake was cooked at 60 minutes.)
Cool on a wire rack 20 to 30 minutes before inverting onto a serving tray.
Cool completely before covering.