- With the rack in the lowest position, preheat the oven to 180 °C (350 °F).
- Line the bottom of a 20-cm (8-inch) springform pan with parchment paper and butter thoroughly.
- Spread the melted butter then the brown sugar into the pan. Arrange the plums, skin side down. Scatter the pecans evenly between the plums.
- In another bowl, combine the flour, baking powder and nutmeg. Set aside.
- In a large bowl, cream the butter, sugar and vanilla with an electric mixer until smooth. Whisk in the egg.
- Stir in half of the dry ingredients. Add the milk and finish with remaining dry ingredients. Gently spread the batter over the plums.
- Bake for about 1 hour and 15 minutes or until a toothpick inserted in the centre of the cake comes out clean. Cool for one hour on a rack before removing from the pan. Run the blade of a knife inside the pan, flip and unmould onto a plate.
- At service, top each portion with whipped cream or vanilla ice cream.