1.Preheat oven to 180°C/350°F. Grease a deep 22cm (9-inch) square cake pan.
2.Beat eggs and sugar in a small bowl with an electric mixer about 10 minutes or until thick and creamy and sugar has dissolved; transfer to a large bowl.
3.Sift dry ingredients twice, then sift a third time over egg mixture; fold dry ingredients into egg mixture. Spread mixture into pan.
4.Bake sponge about 25 minutes. Turn immediately onto a baking-paper-covered wire rack, then turn top-side up to cool.
5.Meanwhile, make raspberry glacé icing. Push raspberries through a fine sieve into a small heatproof bowl; discard solids. Sift icing sugar into same bowl; stir in butter and enough of the water to make a thick paste. Place bowl over a small saucepan of simmering water; stir mixture until icing is spreadable.
6.Beat cream in a small bowl with an electric mixer until soft peaks form.
7.Split sponge in half; use a serrated or electric knife to split and cut the sponge. Place bottom half of sponge on a serving plate or stand; spread with jam and cream. Top with remaining sponge half; spread top with icing. Serve topped with fresh rose petals, if you like.
Filled, this sponge is best eaten the day it is made.Note