In a saucepan, combine the oats, water or milk, and cinnamon.
Bring to a boil over medium heat, then reduce heat and simmer for 5-7 minutes, or until the oats reach desired consistency (creamy or slightly al dente).
Remove from heat and stir in the sliced banana.
Add a pinch of salt to taste, if desired.
Enjoy warm, topped with your favorite additional ingredients like nuts, seeds, or dried fruit.