4 Gently stir in the milk, lemon zest and vanilla. Sift the flour and baking powder together then fold into the mixture.
5 Spoon into the tin and bake for 35 minutes. Test with a skewer - if it is clean when removed, the cake is ready.
6 Melt the extra measure of butter then when bubbling add the remaining 200g of sliced plums. Cook for three minutes or until soft, then top the cake and sprinkle with icing sugar. Serve with yoghurt.