Preheat the oven to 350°F. Prepare your 10 cup bundt pan (I use the spray with flour in it, but you can butter and flour your pan if you prefer.)
Mix together the lemon rind and the lemon juice and set aside.
In a mixing bowl, whisk together the flour, baking powder and cornstarch until mixed and lump free.
In your mixer, beat butter until soft and creamy. Add 3/4 cup of sugar and cream for a couple of minutes.
Add the 6 egg yolks and beat on high speed for at least 5 minutes.
Turn the mixer to low and add half of the flour mixture, mixing until just incorporated. Then add the lemon juice and zest again mixing until incorporated, but no longer. Stir the last of the flour and cornstarch in by hand, mixing until smooth.
In a separate bowl, beat 6 egg whites and salt until they hold a soft shape. Slowing add in remaining 1/4 cup of sugar and beat until they form soft peaks.
Add about 1/4 of the egg white mixture to the batter and fold it in to lighten the batter. Keep adding the egg whites, about 1/4 at a time, folding until just mixed until the egg white mixture is all folded in. Be sure to mix as little as possible along the way so as to not deflate the whites completely.
Scoop into the prepared pan and smooth out the top.
Bake for 40-45 minutes or until the top is golden brown and the cake springs back then you press it with a finger.
Remove the pan from the oven, but do not unmold the cake until it is completely cooled. Then turn it onto a plate and refrigerate until it is firm enough to handle. Wrap in plastic wrap and refrigerate overnight.
It is displayed beautifully with a sprinkling of powdered sugar and cut into thin slices.
Maida suggest serving 2-3 thin slices per portion. Great served with: powdered sugar, berries and cream cheese whipped cream