Preheat oven to 375 degrees F (190 degrees C). Wash angel food tube pan in hot soapy water to ensure it is totally grease free. Let dry completely. Sift flour and 3/4 cup confectioners' sugar together three times; set aside.

In mixing bowl, beat egg whites and salt on high speed until foamy. Add cream of tartar, 1 teaspoon vanilla, and almond flavoring; beat until soft peaks form. Peaks should be soft enough so they bend over slightly at the tips. Gradually add 1 cup white sugar, continuing to beat until stiff peaks form. Sift about 1/4 of the flour mixture over the egg whites, and using flat spatula, quickly but gently fold into egg whites. Repeat using 1/4 of the flour mixture each time. Pour batter into clean tube pan. Gently cut through batter with knife to remove air pockets.

Bake for about 30 to 35 minutes, until an inserted wooden pick comes out clean. Invert pan onto a wire rack to cool for 1 hour.

Beat 2 cups confectioners' sugar, butter, cream, and 1 teaspoon vanilla together until smooth. Add more cream or confectioners' sugar as needed. Frost the cooled cake.