1. Heat oven to 350 degrees with a rack in middle position. Grease a 13x18" rimmed baking sheet and set aside.
2. In a medium bowl, whisk 3 cups (12 3/4 ounces) plus 2 tablespoons flour, the baking powder, and salt; set aside. In a large bowl, beat 2 cups granulated sugar, 8 tablespoons butter, and 2 teaspoons vanilla with an electric mixer on medium until light and fluffy. Add eggs one at a time, beating well after each addition.
3. Add one-third of dry ingredients to butter mixture and beat well, then add half of milk; beat well. Repeat with another one-third of dry ingredients, followed by remaining half of milk and remaining dry mixture, beating well after each addition. Scrape batter onto prepared baking sheet and spread into an even layer. Bake until lightly golden and nearly cooked through, 20 to 25 minutes.
4. Meanwhile, make the topping: Melt remaining 4 sticks butter, then combine with the cinnamon and remaining 3 teaspoons vanilla in a large bowl. Stir in remaining 1 1/2 cups sugar until well incorporated, then stir in remaining 4 cups (17 ounces) flour until mixture is crumbly and no streaks remain.
5. Transfer cake pan to a wire rack. Beginning with sides of cake, sprinkle crumb mixture evenly over top. Return to oven and bake until crumbs are golden, about 20 more minutes. Let cool completely. Dust with confectioners' sugar before serving.
Source: Hannaford fresh Magazine, March-April 2023