Have one very clean, ungreased 10” tube pan at the ready (see Note). Sift the sugar into a bowl. Scoop out a ¼ cup of it, sift it three times with the flour, and then place that mixture in second bowl.
Preheat the oven to 350 degrees F. Place the egg whites, water, lemon juice and cream of tartar in the very clean bowl of your stand mixer. Beat until soft, wet looking peaks form. Fold in the extracts.
Beat the remaining ½ cup sifted sugar, 1 Tbsp. at a time, into the egg whites. When all the sugar has been added, the meringue mixture will be quite white, glossy and have peaks that slightly bend over at their points.
Sprinkle ¼ of the sifted flour/sugar mixture over the meringue. With a very clean rubber spatula, very gently fold it in (do not vigorously stir!). Repeat this step until all the flour/sugar mixture is incorporated.
Spoon the batter into the pan and very gently spread to level the top. Bake 45 minutes. Carefully invert the cake pan, while still hot, onto a baking rack. Let cool upside down for at least 2 hours.
To unmoulded, run a sharp, thin-bladed knife or thin metal spatula around the outside edges of the pan to loosen the cake. Set a cake plate over the pan, and then invert and let the cake slip out on to it. Use a sharp serrated knife or angel food cake cutter to cut the cake into portions. Serve the cake, if desired, with whipped cream and fresh berries.
Note: Cake and pastry flour is sold in bags in the baking supply aisle. To get the 1 cup sifted flour needed for this recipe, measure and then sift 2 cups of flour into a bowl. Remove the one-cup of sifted flour needed for the cake; return the rest of the flour to its storage container.
A tube pan, is a round, flat-sided, cake pan with a hollow, cone-shaped centre. It is sold at stores selling a good selection of kitchenware. It is not a bundt pan, which has a fluted design that will make an angel food cake impossible to unmould.