1. Preheat the oven to 350°F and grease a 9×13-inch baking dish.

2. In a large bowl, mix the yellow cake mix, eggs, water, and vegetable oil until smooth.

3. Pour the batter into the prepared baking dish and spread it evenly.

4. In a separate bowl, stir together the melted butter, brown sugar, and ground cinnamon.

5. Drop spoonfuls of the cinnamon mixture over the batter and gently swirl with a knife.

6. Bake for 28 to 32 minutes, until the cake is set and lightly golden.

7. Let the cake cool for 10 minutes, then poke holes all over the top with the handle of a wooden spoon.

8. Slowly pour the sweetened condensed milk over the warm cake, letting it sink into the holes.

9. Cool the cake completely.

10. Beat the softened cream cheese until smooth, then mix in the powdered sugar, vanilla extract, and milk until creamy.

11. Spread the frosting over the cooled cake.

12. Slice and serve chilled or at room temperature.