Grease and line a 1 kg (2 lb) loaf tin. Place all the cake ingredients in a food processor and whiz until smooth, or beat in a large bowl.
Pour the mixture into the prepared tin and place in a preheated oven, 180°C (350°F), Gas Mark 4, for 35–40 minutes until golden and firm to the touch. Remove the cake from the oven and transfer to a wire rack.
Prick holes all over the sponge with a cocktail stick. Place the drizzle ingredients in a bowl and mix together, then drizzle the liquid over the warm loaf. Leave until completely cold. Decorate with a twist of lemon rind, if desired.