Preheat oven to 350°F (175°C). Grease a 9x13-inch baking pan. In large bowl, whisk flour, sugar, baking powder and salt. Add milk, eggs, vanilla and melted butter. Mix until smooth.
Make Cinnamon Swirl
Preheat oven to 350°F (175°C). Grease a 9x13-inch baking pan. In large bowl, whisk flour, sugar, baking powder and salt. Add milk, eggs, vanilla and melted butter. Mix until smooth.
Make Cinnamon Swirl
In small bowl, mix softened butter, brown sugar and cinnamon into paste. Drop spoonfuls evenly over cake batter. Use knife to swirl through batter in figure-8 pattern.
Bake the Cake
Bake for 25-30 minutes until toothpick comes out clean. Cool slightly before frosting.
Prepare Frosting
Beat cream cheese and butter until smooth. Add powdered sugar, vanilla and milk. Beat until creamy. Drizzle over warm cake.
Notes
For extra gooey texture, poke holes in warm cake before frosting. Store covered at room temperature for 2 days or refrigerate for 5 days.