Grease a 9x13 pan.
Melt the butter over medium low heat in a saucepan. Add 1 cup brown sugar and stir until dissolved. Pour into the greased pan.
Tear bread into 2 inch cubes. Place in pan evenly about 2 inches thick.
Beat eggs, milk, and vanilla extract in a bowl. Pour over the bread. Use a spoon or your fingers to ensure that all of the bread is coated evenly.
Sprinkle cinnamon on top.
Cover and place in the fridge for several hours. You can also leave it in the fridge overnight.
Bake at 450 degrees F for 15 minutes. Reduce heat to 350 F and bake an additional 30 minutes.
