Instructions

• Preheat oven to 375°F (190°C). Spray a 9×13-inch baking pan with nonstick cooking spray.
• Make the cinnamon filling: in a small bowl whisk together 2/3 cup (134 g) packed brown sugar, 1/4 cup (31 g) all-purpose flour, and 2 teaspoons ground cinnamon until evenly combined. Set aside.
• Make the streusel: in a medium bowl combine 1 cup (200 g) packed brown sugar, 1/4 cup (31 g) all-purpose flour, and 2 teaspoons ground cinnamon. Add 1/4 cup (57 g) melted unsalted butter and stir with a fork until the mixture resembles wet sand. Set aside.
• Whisk the dry cake ingredients: in a small bowl whisk together 3 cups (372 g) all-purpose flour, 1 tablespoon baking powder, and 1 teaspoon salt. Set aside.
• Make the cake batter: in a large bowl use a hand mixer on medium speed to beat 1/2 cup (113 g) melted unsalted butter and 1 1/2 cups (300 g) granulated sugar until combined (the mixture will be grainy). Mix in 2 large eggs and 1 teaspoon vanilla extract until incorporated. Stir in 1 cup (237 ml) milk. Add the flour mixture and stir just until combined—do not overmix.
• Assemble the cake: spread half of the batter evenly into the prepared 9×13 pan. Evenly sprinkle the reserved cinnamon filling over the batter. Spoon the remaining batter over the filling and spread gently to cover. Evenly sprinkle the streusel over the top.
• Bake in the preheated oven for 30–35 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs. Remove from oven and let cool.
• For best slices, cool completely before cutting. Store cooled cake in an airtight container for up to 3 days. To freeze, slice cooled cake, place in an airtight container, and freeze for up to 1 month.