Lime Syrup Buttermilk Cake

Grease and lightly flour a 20cm baba pan; shake out excess flour. Cream butter, rind and sugar in small bowl with mixer until light and fluffy, beat in egg yolks one at a time, beat until combined. Transfer mixture to large bowl, stir in half the sifted flour and half the buttermilk, then stir in remaining flour and buttermilk. Beat egg whites in small bowl until soft peaks form, fold lightly into mixture in 2 batches. Spread mixture into prepared pan. Bake in moderate oven for about 1 hour. Stand for 5 mins before turning onto wire rack. Pour hot lime syrup evenly over hot cake. Lime Syrup: Combine lime juice, sugar and water in saucepan, stir over heat until sugar is dissolved, bring to the boil; remove from heat. Keeping time : 2 days.