In a medium saucepan, melt the butter over medium heat. Add the diced apples and cook, stirring occasionally, for 3-4 minutes until they begin to soften.

Stir in the ground cinnamon and salt, and cook for another 30 seconds until fragrant. Add the rolled oats to the pan and stir to combine with the apples and spices.

Pour in the milk (or water) and bring the mixture to a simmer. Reduce the heat to low and cook for 5-7 minutes, stirring frequently, until the oatmeal is creamy and has reached your desired consistency.

Remove the oatmeal from the heat and stir in the brown sugar or maple syrup. Serve immediately with your favorite toppings.