First blend the sugar in a mixie until quite fine. Seperate into two halves and keep aside.
In a bowl mix together 1/2 cup of sugar, flour, corn flour, salt, lemon zest together.
Whisk together egg whites with the cream of tartar until stiff. Add remaining sugar to it and whisk until it is glossy. Add the lemon extract to it.
Fold in the flour gently. Try to minimize losing the air from the egg. Pour into a prepared pan and bake for 35 minutes or until a skewer comes out clean.
Serve with whipped cream and fresh fruits.