Pre-heat oven to 180 degrees C (350 degrees F). Wash the plums cut them into halves or quarters - discard the seeds. Lightly grease a 24 cm (9 1/2 inch) cake tin with butter.

Put the eggs into a bowl with the vanilla and the sugar and beat until pale and fluffy. Add the sifted flour and baking powder and mix to incorporate. Whisk in the melted butter and milk

Put a few plums in the bottom of the tin and tip the batter over the top. Top with the remaining plums and sprinkle with the extra sugar.

Bake for approximately 1 hour or until nice and golden. Remove from the oven and let cool in the tin before removing it.

Serve plain, sprinkled with icing sugar or with a dollop of cream, ice-cream or mascarpone cream