¾cup(170g)salted butter, very soft (but not melted)
¾cup(159g)light brown sugar
1tablespoonflour
1tablespoonground cinnamon
Glaze:
2cups(228g)powdered sugar
4-5tablespoonsmilk
½teaspoonvanilla
Instructions
Preheat oven to 350 degrees F. Lightly grease a 9X13-inch baking pan with nonstick cooking spray and set aside.
For the cake, in a large bowl, combine all the cake batter ingredients and mix well. Spread the batter evenly in the prepared pan.
For the swirl, in a medium bowl, stir together the butter, light brown sugar, flour and cinnamon until well-mixed and smooth. Dollop the cinnamon swirl mixture by heaping spoonfuls over the cake batter.
Use a butter knife to swirl the cinnamon mixture into the TOP of the cake batter (don't press the knife all the way to the bottom of the pan - swirl just into the top half of the cake batter). Try not to over swirl or over mix. A few generous loops through the batter should be just fine.
Bake the cake for 30-32 minutes until the top springs back lightly to the touch and a toothpick inserted in the center comes out clean or with a few moist crumbs.
For the glaze, whisk together the powdered sugar, milk and vanilla until smooth. Pour the glaze evenly over the warm cake.