Ingredients:
For the cake:
8 ounces(1 stick) unsalted butter, room temperature, plus more for greasing pan
1/2 cupplus 2 tablespoons granulated sugar, plus more for coating pan
2 large eggs, room temperature
1 tablespoonvanilla bean paste
1 1/2 cupsall-purpose flour
1/2 teaspoonkosher salt
1 1/2 teaspoonsbaking powder
1/2 cupplus 1 tablespoon whole milk, room temperature
For the red wine simple syrup:
1/2 cupred wine
1/2 cupgranulated sugar
For the plum garnish & mascarpone whip:
2 plums, pitted and sliced
3/4 cupheavy whipping cream
2 tablespoonspowdered sugar
6 ouncesmascarpone cheese
1 pinchkosher salt
Directions:
Make the cake: Heat the oven to 350°F. Grease a 9-inch cake pan with butter, then sprinkle in sugar (up to ¼ cup) until lightly coated. Tap out the excess.
Using an electric mixer fitted with the paddle attachment, cream together the butter and sugar in a large bowl on medium speed until light and fluffy, about 1 minute. Add the eggs one at a time, plus the vanilla bean paste, scraping down the bowl in between additions. In a separate bowl, whisk together the flour, salt, and baking powder. Alternating between the two, add half of the flour mixture, then half of the milk to the butter-egg mixture. Mix on medium-low speed until just combined and no flour pockets remain. Transfer the batter to the pan. Bake in the oven, 30 to 40 minutes, or until a toothpick inserted in the center comes out clean. Transfer the cake pan to a cooling rack and let cool, removing the cake from the pan after about 15 minutes.
Make the red wine simple syrup: In a small pot, combine the wine and sugar. Heat over medium heat, stirring occasionally, until the sugar has dissolved and the liquid has slightly reduced, about 7 to 9 minutes. Set aside to cool.
Make the plum garnish: Once the red wine syrup has cooled, about 15 minutes, transfer ⅔ of the glaze to a large, shallow bowl. Add the plums to the bowl and allow to infuse for at least 30 minutes and up to 3 hours.
Make the mascarpone whip: Using an electric mixer fitted with the whisk attachment, beat the cream and sugar until peaks begin to form. Add the mascarpone and salt, continuing to whip until soft peaks form.
Assemble the cake: If the cake has domed during baking, trim the top using a serrated knife so it is flat. Using a pastry brush, dab the remaining wine glaze over the top of the cake until evenly coated.
Top the cake with the mascarpone whip, swirling using a spatula. Arrange the soaked plums in a circle around the cake. Serve at room temperature, or store in an airtight container in the refrigerator for up to 3 days.