How to Make It
Preheat the oven to 350°. Butter a 10-inch springform pan. Line the bottom with parchment paper and butter and flour the paper and pan. In the bowl of a standing mixer fitted with the paddle, beat the eggs at medium-high speed for 5 minutes, until fluffy. Add the zest and 1 cup of the sugar and beat at high speed until the mixture is pale and fluffy and leaves a ribbon trail when the paddle is lifted, about 15 minutes.
Meanwhile, in a food processor, combine the flour and salt with 2/3 cup of the almonds and process until the nuts are very finely ground. Scrape into a medium bowl. Add the remaining 1/2 cup of sugar and 1 1/3 cups of almonds to the processor and process until the mixture is very finely ground and beginning to clump. Add to the flour mixture and whisk to combine, breaking up any large clumps.
Using a rubber spatula, fold the dry ingredients into the egg mixture in 3 batches until fully incorporated. Pour the batter into the prepared pan and gently smooth the surface. Bake the cake for 45 minutes, or until a toothpick inserted in the center comes out clean. Transfer to a rack and let cool completely.
Meanwhile, in a large, deep skillet, combine the wine, rum, water, sugars, citrus zests, vanilla bean and seeds, cinnamon, cloves and star anise. Add the plums, cut sides down, and bring to a simmer over moderately high heat. Reduce the heat and simmer for 20 minutes, turning the plums every 5 minutes. With a slotted spoon, transfer the plums to a baking sheet to cool. Continue to simmer the liquid until reduced to about 1 cup, about 3 minutes. Strain the syrup through a sieve into a heatproof bowl, pressing on the solids.
Using your fingers or a paring knife, pull off the skins from the plums. Slice the plums into wedges and transfer to a serving bowl. Pour the syrup over the plums and toss to coat. Let cool to room temperature.
Run a knife along the side of the cake; remove the ring. Invert the cake onto a platter and peel off the parchment. Dust the cake with confectioners’ sugar and cut into wedges. Serve with the plum compote and sweetened crème fraîche.
The cake can be kept covered at room temperature for up to 2 days. The plum compote can be refrigerated overnight; serve at room temperature.