Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish.

Whisk together all-purpose flour, granulated sugar, baking powder, and salt in a large bowl.

Combine the milk, eggs, and vanilla in another bowl, mixing until smooth. Stir this wet mixture into the dry ingredients and gently fold in melted butter.

Pour the batter into your prepared baking dish, spreading it evenly.

Mix brown sugar, melted butter, and ground cinnamon in a small bowl until smooth. Drop spoonfuls of the cinnamon mixture over the batter and gently swirl with a knife.

Bake for 32–35 minutes or until a toothpick inserted in the center comes out clean.

Cool the cake completely in the pan on a wire rack.

Beat cream cheese, softened butter, and vanilla until fluffy. Gradually mix in powdered sugar.

Spread frosting over the cooled cake and lightly dust with cinnamon before serving.