In a saucepan, combine the egg, yolks, sugar, lemon zest and juice. Gently bring to a simmer on medium heat stirring continuously to ensure that all ingredients mix well.

Keep stirring and cook for about 5 minutes till the mixture starts to thicken to a custard-like consistency.

Stir in the butter and cook for a minute more or less till thickened to a curd. Remove from the heat immediately and strain through a medium sieve into a clean bowl.

Cover with cling film pressing down on the surface of the curd. This will eliminate all the air and ensure that no skin forms on the surface. Set aside.

Preheat the oven to 180 degrees C and grease and line a 25 cm x 30 cm Swiss roll pan.

Beat the eggs in a bowl till pale and creamy. Add the sugar in batches, beating alternately to dissolve the sugar.

Fold in the flour and the hot water. Pour the batter into the prepared pan and bake for 8-10 minutes.

Turn out the warm roll immediately on a tea towel or parchment. Using a spatula or palette knife, slather generously with lemon curd (reserving about a third). scatter the cherries evenly all over.

Using the short side of the tea towel or parchment, gently but firmly roll the sponge. Transfer carefully on to the serving platter and smother evenly with the remaining lemon curd and decorate with a few cherries. Chill for at least an hour before slicing the roll.