Put the icing sugar in a bowl and add 4 teaspoons of the rosewater or lemon juice. Mix until smooth, adding a little more liquid if necessary until the icing forms a thick paste. Spread over the tops of the cooled cakes.
Knead the red icing on a work surface lightly dusted with icing sugar. Roll out thickly and cut out 12 small heart shapes using a cutter. Place a heart on the top of each cake.
Press the jam through a small sieve to remove any lumps. Put the sieved jam in a small piping bag fitted with a writing nozzle. Pipe small dots into the icing around the edges of each cake and pipe a line of jam around the edge of each heart.