- 2 cups cake flour (not self-rising)
- 1 teaspoon baking powder
- 1 teaspoon baking soda
- 3/4 teaspoon salt
- 1 stick (1/2 cup) unsalted butter, softened
- 1 cup sugar
- 1 teaspoon vanilla
- 2 large eggs
- 1 cup well-shaken buttermilk
- 3/4 cup Beaumes-de-Venise or other white dessert wine
- 4 tablespoons sugar
- 1 (3- by 1-inch) strip fresh orange zest
- 1/3 cup seedless blackberry preserves or 1/2 cup blackberry preserves with seeds, strained
- 4 cups fresh blackberries (1 1/2 lb)
- Preheat oven to 350°F.
- Line bottom of a buttered 9- by 2-inch round cake pan with a round of wax paper, then butter paper.
- Sift together flour, baking powder and soda, and salt. Beat together butter and sugar in a large bowl with an electric mixer until pale and fluffy, then beat in vanilla. Add eggs 1 at a time, beating well after each addition, then, with mixer at low speed, beat in all of buttermilk until just combined. Add flour mixture in 3 batches, mixing after each addition until just combined.
- Spoon batter into cake pan, smoothing top, and bake in middle of oven until golden and a tester comes out clean, 40 to 50 minutes. Cool in pan on a rack 10 minutes, then run a thin sharp knife around edge of cake to loosen. Invert onto rack, then slide cake onto a cake plate.
- Bring wine, 3 tablespoons sugar, and zest to a boil in a small heavy saucepan, stirring until sugar is dissolved. Boil until syrup is reduced to about 2/3 cup, 1 to 2 minutes. Discard zest.
- Reserve 2 tablespoons syrup and pour remainder slowly and evenly over cake (cake will absorb syrup).
- Stir together reserved syrup, preserves, and remaining tablespoon sugar in small saucepan and simmer, stirring occasionally, until thickened slightly, about 1 minute (it should be the consistency of a thick syrup). Put blackberries in a large bowl, then pour preserves mixture over berries. Gently stir berries with a rubber spatula to coat, then pour over cake, mounding blackberries on top.
- Serve warm or at room temperature.