Preheat oven to 350 degrees. Spray a 9x13 baking dish with nonstick spray.
Add all of the ingredients except for the butter to a mixing bowl and whisk well to combine.
Pour in the melted butter and use an electric mixer on low speed, mixing the batter until it’s just combined. Do not overmix.
Pour batter into the prepared baking dish.
To make the topping, whisk together the brown sugar and cinnamon.
Sprinkle the topping over the top of the cake and use a butter knife to swirl the topping into the batter.
Bake for 35-40 minutes or until a tester inserted in the center comes out clean.
Cool for 10 minutes before whisking together the powdered sugar and milk to make the glaze. Add additional milk 1 tablespoon at a time to reach the consistency you prefer. Pour the glaze over the warm cake.
Let glaze set before slicing and serving.
Store the cake tightly covered at room temperature for 3-4 days.