Step 1

Heat the oven to 325°F with a rack in the middle position. Mist the bottom and sides of a 9-inch springform pan with cooking spray, then dust evenly with flour; tap out the excess.

Step 2

In a stand mixer with the paddle attachment, mix the flour, 107 grams (½ cup) of the sugar, the baking powder and salt on low until combined, about 5 seconds. With the mixer running, add the butter 1 piece at a time and continue mixing just until the mixture resembles moist sand, 2 to 3 minutes. Add the egg, egg yolk and vanilla. Increase to medium-high and beat until pale and fluffy, about 1 minute, scraping down the bowl as needed.

Step 3

Transfer the batter to the prepared pan and spread in an even layer. Arrange the plum quarters on top of the batter in 2 concentric circles, placing the pieces on their cut sides.

Step 4

Sprinkle with the remaining 2 tablespoons sugar. Bake until golden brown and a skewer inserted at the center comes out clean, 1 to 1¼ hours.

Step 5

Let cool in the pan on a wire rack for 30 minutes, then remove the pan sides. Serve warm or at room temperature, dusted with powdered sugar.