Preheat the oven to 350°F.

Spray a 9x13" baking pan with cooking spray.

Melt the butter in a saucepan over medium low heat. Whisk in the brown sugar until combined.

Whisk in the eggs, one at a time, allowing each egg to absorb before adding the next one.

Whisk in the vanilla, cinnamon, baking soda and salt.

Fold in the flour until no big flour pockets remain. Don't over mix.

Pour the mixture into the prepared pan and bake for about 15 minutes or until a toothpick comes out with moist crumbs.

Allow to cool for about 20-30 minutes or until it's warm.

Prepare the icing by combining the butter and cream cheese and beating until thoroughly combined. Add in the vanilla and mix. Scrape. Add in the confectioners' sugar in two additions and beat until combined. Add some milk or heavy cream if needed to thin it down to spreadable consistency.

Once the icing is finished, spread the icing evenly over the cinnamon mixture.

Cover and refrigerate for at least an hour or up to overnight.

Make sure you let it come back to room temperature before cutting it, so it'll be easier, especially if you refrigerated overnight.