Add a little bit of flour just make sure that all the surface of the baking dish is covered with the flour
Pour the half of your batter into the prepared baking dish and sprinkle half of brown sugar all over the top of your batter
pour the remaining batter along with the remaining brown sugar and bake the cake to the oven until it is cooked well.
Remove it from the oven and let the cake cools on the baking dish
Pour the frosting all over the top of your cake and using the back of your spoon or using a spatula smooth the surface just to make sure that all the frosting is distributed well
Add a little bit of flour just to cover the baking dish.