Pour half of the red velvet cake batter into the baking dish. Spreading it out as evenly as possible.
Then, using the spoon, just swirl it around lightly.
Now add the rest of the red velvet cake batter on top and spread it out as evenly as possible.
Do your best to spread it out and cover the cream cheese layer.
Add in powdered sugar and mix until smooth.
Then stir in vanilla.
And lastly, mix in the milk.
Mix until smooth then spread on cooled cake.