Preheat the Oven: Start by preheating your oven to 350°F (175°C). Grease and flour a 9x13 inch baking dish.
Prepare the Cake Batter: In a large mixing bowl, combine the all-purpose flour, granulated sugar, baking powder, and salt. Whisk together until well blended.
Mix Wet Ingredients: In another bowl, whisk together the milk, melted butter, eggs, and vanilla extract until smooth. Slowly pour the wet ingredients into the dry ingredients, stirring just until combined. Be careful not to overmix.
Prepare the Cinnamon Swirl: In a small bowl, mix together the brown sugar, ground cinnamon, and softened butter until you have a crumbly mixture.
Layer the Cake: Pour half of the cake batter into the prepared baking dish. Sprinkle half of the cinnamon swirl mixture over the batter. Pour the remaining batter on top, and finish with the rest of the cinnamon swirl mixture, swirling it gently into the cake batter with a knife for a marbled effect.
Bake the Cake: Place the baking dish in the preheated oven and bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
Prepare the Cream Cheese Glaze: While the cake is baking, prepare the glaze by beating the softened cream cheese with a hand mixer. Gradually add the powdered sugar, then mix in the milk and vanilla extract until smooth and creamy.
Cool and Glaze: Once the cake is done baking, allow it to cool in the pan for about 10 minutes. Then, drizzle the cream cheese glaze over the warm cake before slicing.
Serve: Cut the cake into squares and serve warm or at room temperature. Enjoy your Sweet and Satisfying Instant Cinnamon Roll Cake with a cup of coffee or tea!