Preheat oven to 180°C (350°F) conventional (see note 1 if using a convection oven with a fan) and have a 10-inch tube pan ready (do not grease or line it - leave as is).
Sift together flour, cornstarch and powdered sugar. Using a whisk or fork, mix until well combined. Set aside for now, but keep the sieve handy as the dry ingredients will be sifted a second time.
To a large mixing bowl, add in egg whites, cream of tartar and salt. Using a hand or stand mixer on a medium-high speed (if using a stand mixer use the whisk attachment), whip for 30 seconds until frothy, then gradually add in white granulated sugar - about a tablespoon at a time. Once all the sugar is added in, continue to whip until you reach soft peaks that hold their shape (see note 2). This should take roughly 5-7 minutes depending on the size and power of your mixer.
Next add vanilla and almond extract/essence to the egg whites and mix on a low speed until well combined. Do not overmix.
Sift the dry ingredients from earlier into the egg whites in three batches, gently folding in each batch with a spatula until just combined. Do not overmix (see note 3). You should end up with a thick, almost melted marshmallow like batter.
Distribute the batter evenly into the 10-inch tube pan. Gently smooth out the top with a spatula and then run a skewer or knife through the batter to remove any large air bubbles. Smooth out the top again if needed, give the tin a little shake and then drop it twice on the counter. Bake for 35 minutes, or until the top is set and slowly springs back when you touch it. You can also check with a skewer and if it comes out clean the cake is done.
Immediately turn the cake pan upside down and allow it to completely cool. If you leave the cake upright, it will likely collapse - so don't forget this very crucial step!
Once cool, run a thin knife or spatula around the outer edge and inner edge of the tube pan and invert the cake onto a serving plate/cake stand.
Cut with a serrated knife in a gentle sawing motion to prevent squashing the cake. Serve with whipped cream and berries!