For the topping
16 tablespoons unsalted butter, cut into 6 pieces
½ cup granulated sugar
¾ cup firmly packed light brown sugar
1½ teaspoons ground cinnamon
¼ teaspoon ground nutmeg
Pinch of table salt
2⅔ cups all-purpose flour
For the cake
3 cups all-purpose flour
1¼ cups granulated sugar
1½ teaspoons baking powder
1½ teaspoons table salt
2 large eggs
1 cup whole milk
12 tablespoon unsalted butter, melted and cooled slightly.
2 teaspoons pure vanilla extract
To make the topping:
1. In a large saucepan, melt the butter over medium heat. Slide the pan from the heat and add the granulated sugar, brown sugar, cinnamon, nutmeg, and salt. Stir with a rubber spatula, pressing when necessary, until there are no lumps of sugar. Add the flour and mix until well blended and pasty. Set aside.
To make the cake
2. Position an oven rack on the middle rung. Heat the oven to 350 F. Lightly grease the bottom and sides of a 9 x 13-inch baking pan or dish.
3. In a large bowl, combine the flour, granulated sugar, baking powder, and salt. Whisk until well blended. In a medium bowl, combine the eggs, milk, melted butter and vanilla. Whisk until well blended.
4. Pour the wet ingredients over the dry ingredients and gently stir with a rubber spatula just until blended. Scrape the batter into the prepared pan and spread evenly. Break up the topping mixture with your fingers into medium-sized pieces and sprinkle evenly over the cake batter to form a generous layer.
5. Bake until the cake springs back when lightly pressed in the center and a toothpick or cake tester inserted in the center comes out clean, about 40 minutes. Transfer the pan to a rack to cool. Serve warm or at room temperature. Before serving, sift some confectioners’ sugar over the top, if desired.