Preheat the oven to 350°. Have ready an ungreased 9 or 10-inch tube pan.
In a bowl, sift the dry ingredients together 3 times. (The cake flour, 3/4 cup sugar, and the salt.) Set aside.
In a large, spotlessly clean bowl (you don't want a trace of grease, otherwise the egg whites won't stiffen properly), beat the wet ingredients on low speed for about 1 minute. (The egg whites, water, lemon juice, cream of tartar, vanilla, and almond extract.)
Increase the mixer speed to medium (no high) and beat until the mixture increases in volume 4 1/2 to 5 times and resembles a bowl of slightly translucent foam composed of tiny bubbles. (This takes anywhere from 1 1/2 to 3 minutes.) The foam will hold a very soft, moist shape when the beaters are lifted.
Beat in gradually (on medium speed), 1 Tbsp at a time, taking 2 to 3 minutes: 3/4 cup white sugar.*When all the sugar has been added, the foam will be creamy white and hold soft, moist, glossy peaks that bend over at the points; do not beat until stiff. (If the bowl is nearly full, transfer the mixture to a wide 4-6 qt bowl for easier folding.)
Sift a fine layer of the flour mixture (about 1/8 of the total) evenly over the surface of the batter and fold gently with a rubber spatula only until the flour is almost incorporated. Do not stir or mix.
Repeat 7 more times, folding in the last addition until no traces of flour are visible.
Pour the batter into the pan and tilt or spread to level the top.
Bake until a toothpick inserted in the center comes out clean - 35-40 minutes.
Let cool upside down for at least 1 1/2 hours, set the tube over a bottleneck or rest the pan on 4 glasses (if the pan doesn't have legs).