Draining the rhubarb keeps the cake from becoming soggy.

　　

Ingredients

Makes one 4 1/4 x 13 3/4-inch cake

　　4 tablespoons unsalted butter, softened, plus more for the pan

　　1/2 cup all-purpose flour, plus more for the pan

　　5 ounces rhubarb, cut into 1/4-inch-thick slices (scant 1 1/2 cups)

　　1 cup plus 1 tablespoon sugar

　　1/2 teaspoon baking powder

　　Pinch of coarse salt

　　2 large eggs

　　1 vanilla bean

　　1 large handful blackberries (about 1/3 cup)

　　

Step 1

Preheat the oven to 350°F. Butter and flour a 4 1/4 × 13 3/4-inch fluted tart pan with a removable bottom. Combine the rhubarb and 1/3 cup sugar in a medium bowl, and allow to sit, stirring occasionally, until the rhubarb has released its juice and the sugar has dissolved, about 45 minutes.

　　

Step 2

Sift the flour, baking powder, and salt into a small bowl; set aside. Cream the butter with 2/3 cup sugar in the bowl of an electric mixer fitted with the paddle attachment. Add the eggs, 1 at a time, beating well after each addition. Slice the vanilla bean in half lengthwise. Scrape the seeds from the pod, and add the seeds to the mixture. Beat to combine. Add the reserved flour mixture, and beat to combine. Using a rubber spatula, spoon the batter into the prepared pan, and spread flat.

　　

Step 3

Strain the rhubarb, discarding the juice; add the blackberries, and toss to combine. Spoon the fruit on top of the batter in the pan, sprinkle with the remaining tablespoon sugar, place in the oven, and bake until the cake is golden and center is set, about 1 hour. Remove from the oven, and place on a wire rack to cool slightly before removing the tart pan.

　　Reprinted with permission from The Martha Stewart Living Cookbook: The New Classics by Martha Stewart Living Magazine, copyright © 2007. Published by Clarkson Potter, a division of The Crown Publishing Group.Buy the full book from Amazon.