01 -
Warm your oven to 350°F and coat a 9x13 baking pan with cooking spray to stop sticking.
02 -
Grab a big bowl and throw in flour, sugar, baking powder, eggs, vanilla and milk. Beat everything with your hand mixer until smooth. Switch to low speed and pour in your melted butter bit by bit, mixing as you go. Dump this mix into your greased pan.
03 -
Take a medium bowl and mash together soft butter, brown sugar, flour and cinnamon until you've got a smooth paste.
04 -
Plop spoonfuls of your cinnamon mix onto the cake batter. Grab a butter knife and drag it around making pretty swirly patterns through both mixtures.
05 -
Pop it in the oven for about 35-40 minutes. You'll know it's done when you stick a knife in the middle and it comes out clean.
06 -
In a smaller bowl, stir powdered sugar, milk, and vanilla together until it's nice and smooth.
07 -
Pour your sweet topping all over the cake while it's still warm. Cut into squares and dig in. So good!