1-Getting started: Begin by preheating your oven to 350°F and preparing a 9×13-inch baking dish with nonstick cooking spray. In a large bowl, mix together 3 cups all-purpose flour, 1 cup white granulated sugar, 4 teaspoons baking powder, 2 large eggs, 2 teaspoons vanilla extract, and 1 ½ cups milk until well combined.

2-Add butter: Next, slowly add ½ cup melted salted butter to the mixture, stirring just until everything blends without overmixing. This keeps the cake tender and prevents toughness. Spread the batter evenly into your prepared dish for an even bake.

3-Prepare filling and bake: For the filling, combine ¾ cup softened salted butter, 1 cup packed light brown sugar, 2 tablespoons all-purpose flour, and 1 tablespoon ground cinnamon in a small bowl. Drop spoonfuls of this mixture onto the batter and use a butter knife to swirl it through, creating those signature marble patterns. Bake for 35 to 40 minutes, or until a knife inserted in the center comes out clean.

4-Prepare glaze and finish: While the cake bakes, whisk together 2 cups powdered sugar, 5 tablespoons milk, and 1 teaspoon vanilla extract to make the glaze. Adjust its thickness as needed by adding more sugar or milk. Once baked, pour the glaze over the warm cake and let it cool slightly before serving. For more insights on achieving moist results, visit this tips for making moist cakes resource.