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.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.