Crumb Cake

Ingredients:

Crumb Topping:

• 1/3 cup granulated sugar (2 2/3 ounces)
• 1/3 cup dark brown sugar (2 2/3 ounces)
• 3/4 teaspoon ground cinnamon
• 1/8 teaspoon table salt
• 8 tablespoons unsalted butter (1 stick), melted and still warm
• 1 3/4 cups cake flour (7 ounces)

Cake:

• 1 1/4 cups cake flour (5 ounces)
• 1/2 cup granulated sugar (3 1/2 ounces)
• 1/4 teaspoon baking soda
• 1/4 teaspoon table salt
• 6 tablespoons unsalted butter (3/4 stick), cut into 6 pieces, softened but still cool
• 1 large egg
• 1 large egg yolk
• 1 teaspoon vanilla extract
• 1/3 cup buttermilk
• Confectioners’ sugar for dusting

Instructions:

• For the topping: Whisk sugars, cinnamon, salt, and butter in medium bowl to combine. Add flour and stir with rubber spatula or wooden spoon until mixture resembles thick, cohesive dough; set aside to cool to room temperature, 10 to 15 minutes.
• Adjust oven rack to upper-middle position and heat oven to 325 degrees. Cut 16-inch length parchment paper or aluminum foil and fold lengthwise to 7-inch width. Spray 8-inch square baking dish with nonstick cooking spray and fit parchment into dish, pushing it into corners and up sides; allow excess to overhang edges of dish.
• In bowl of standing mixer fitted with paddle attachment, mix flour, sugar, baking soda, and salt on low speed to combine.
• With mixer running at low speed, add butter one piece at a time; continue beating until mixture resembles moist crumbs, with no visible butter chunks remaining, 1 to 2 minutes.
• Add egg, yolk, vanilla, and buttermilk; beat on medium-high speed until light and fluffy, about 1 minute, scraping once if necessary.
• Transfer batter to baking pan; using rubber spatula, spread batter into even layer.
• Break apart crumb topping into large pea-sized pieces and spread in even layer over batter, beginning with edges and then working toward center.
• Bake until crumbs are golden and wooden skewer inserted into center of cake comes out clean, 35 to 40 minutes.
• Cool on wire rack at least 30 minutes. Remove cake from pan by lifting parchment overhang. Dust with confectioners’ sugar just before serving.