Preheat oven to 325 degrees F.
Separate eggs carefully, putting whites in a large mixing bowl and yolks in another large mixing bowl. Beat egg yolks until light and foamy. Slowly add the water. Gradually beat in the sugar, then vanilla and/or almond extract; 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 and fold flour mixture 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 tartar. Increase the mixer speed and beat until they form moist, glossy peaks.
Pour the egg yolk mixture in thin stream over the entire surface of the egg white mixture, gently cutting and folding with rubber spatula, making sure everything is completely folded. Pour into an ungreased 10-inch round tube pan with a removable bottom. Draw a thin spatula gently through the batter to get rid of any large air pockets.
Bake on the second rack from the bottom of the oven for 1 hour. (The cake tends to fall a small amount after 50 minutes, so do not worry.)
Invert pan onto a rack and let cool out of the pan for 1 1/2 hours. Frost when cake is completely cooled. If desired, garnish cake with orange peel or zest.
Combine butter and sugar in a medium bowl. Add just enough orange juice to thin the frosting to a spreading consistency.