Preheat oven to 325°. Separate eggs carefully, putting whites in a large mixing bowl, yolks in another large mixing bowl. Beat egg yolks until light and foamy. Slowly add water. Gradually beat in sugar, then vanilla (and/or almond) and beat until pale and thick in texture (total beating time can be as long as 7 minutes). Sift flour again with salt and baking powder. Return to sifter; fold into egg yolk mixture, sifting in a little at a time.
Beat egg whites gently until foamy. Add a pinch of salt and the cream of tarter. Increase mixer speed and beat until they form moist, glossy peaks.
Pour egg yolk mixture in thin stream over entire surface of egg white mixture, gently cutting and folding with rubber spatula, making sure everything is completely folded. Pour into Ungreased 10-inch round tube pan, (removable bottom). Draw a thin spatula gently through the batter to destroy any large air pockets.
Bake in slow oven (325°) on second rung from bottom for 60 minutes (tends to fall a small amount at 50 minutes).
Invert pan to cool 1 1/2 hours. Frost when cool.
Orange Butter Cream Frosting:
Mix butter with powder sugar. Carefully add enough orange juice to thin for spreading. Garnish with orange zest or peel, if desired.