Preheat the oven: Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking pan to ensure the cake doesn’t stick as it bakes.
Make the cake batter: In a large bowl, mix together the melted butter, eggs, sugar, flour, vanilla extract, baking powder, salt, and milk. Stir until everything is well combined and the batter is smooth. The batter should be thick but pourable.
Pour the batter into the pan: Pour the cake batter into the prepared 9×13-inch pan, spreading it evenly with a spatula to cover the entire bottom.
Prepare the topping: In a small bowl, mix together the melted butter, brown sugar, flour, and cinnamon until smooth. This will create a delicious cinnamon-sugar mixture to swirl into the batter.
Apply the topping: Spoon the cinnamon-sugar topping evenly over the batter. Use a knife or a skewer to gently swirl the topping into the cake batter, creating a beautiful marbled effect.
Bake the cake: Place the pan in the oven and bake for 30–35 minutes, or until the cake is golden brown and a toothpick inserted into the center comes out clean. The cake should be firm to the touch and lightly browned on top.
Make the glaze: While the cake is baking, prepare the glaze. In a small bowl, whisk together the powdered sugar, milk, and vanilla extract until smooth. The glaze should have a consistency similar to pancake syrup, not too thick but pourable.
Drizzle the glaze: Once the cake is baked and slightly cooled (about 10 minutes), drizzle the glaze generously over the top while the cake is still warm. The glaze will set into a slightly firmer texture as it cools, adding a sweet finish to the cake.
Serve and enjoy: Allow the cake to cool slightly before serving. It can be enjoyed warm or at room temperature. Serve it as a breakfast treat, a brunch dish, or even as a dessert to share with friends and family!
