SERVES 8 TO 10
Don’t be tempted to substitute all-purpose flour for the cake flour; doing so will make a dry, tough cake. If you can’t find buttermilk, you can use an equal amount of plain low-fat yogurt, but do not substitute powdered buttermilk because it will make a sunken cake. When topping the cake, take care to not push the crumbs into the batter. This recipe can be easily doubled and baked in a 13 by 9-inch baking dish. If doubling, increase the baking time to about 45 minutes.
CRUMB TOPPING |
|
⅓ |
cup (2⅔ ounces) granulated sugar |
⅓ |
cup packed (2⅓ ounces) dark brown sugar |
¾ |
teaspoon ground cinnamon |
⅛ |
teaspoon table salt |
8 |
tablespoons (1 stick) unsalted butter, melted and still warm |
1¾ |
cups (7 ounces) cake flour (see note) |
CAKE |
|
1¼ |
cups (5 ounces) cake flour (see note) |
½ |
cup (3½ ounces) granulated sugar |
¼ |
teaspoon baking soda |
¼ |
teaspoon table salt |
6 |
tablespoons (¾ stick) unsalted butter, cut into 6 pieces, softened but still cool |
1 |
large whole egg plus 1 large egg yolk |
⅓ |
cup buttermilk (see note) |
1 |
teaspoon vanilla extract |
Confectioners’ sugar, for dusting |
|
1. FOR THE CRUMB TOPPING: Whisk the sugars, cinnamon, salt, and butter together in a medium bowl to combine. Add the flour and stir with a rubber spatula or wooden spoon until the mixture resembles a thick, cohesive dough; set aside to cool to room temperature, 10 to 15 minutes.
2. FOR THE CAKE: Adjust an oven rack to the upper-middle position and heat the oven to 325 degrees. Cut a 16-inch length of parchment paper or aluminum foil and fold lengthwise to a 7-inch width. Spray an 8-inch square baking dish with vegetable oil spray and fit the parchment into the dish, pushing it into the corners and up the sides; allow the excess to overhang the edges of the dish.
3. In the bowl of a stand mixer fitted with the paddle attachment, mix the flour, sugar, baking soda, and salt on low speed to combine. With the mixer running at low speed, add the butter one piece at a time; continue beating until the mixture resembles moist crumbs, with no visible butter chunks remaining, 1 to 2 minutes. Add the egg, egg yolk, buttermilk, and vanilla; beat on medium-high speed until light and fluffy, about 1 minute, scraping once if necessary.
4. Transfer the batter to the prepared baking pan; using a rubber spatula, spread the batter into an even layer. Break apart the crumb topping into large pea-size pieces, rolling them between your thumb and forefinger to form crumbs, and spread in an even layer over the batter, beginning with the edges and then working toward the center. Bake until the crumbs are golden and a wooden skewer inserted into the center of the cake comes out clean, 35 to 40 minutes. Cool on a wire rack for at least 30 minutes. Remove the cake from the pan by lifting the parchment overhang. Dust with confectioners’ sugar before serving.