First, spray a 8x8 baking dish with cooking spray and preheat your oven to 350 degrees.
In a large bowl, mix together the apples, sugar, flour, salt and cinnamon. Make sure all the apples are coated well, then place apples into prepared baking dish.
To make the topping, use a medium bowl and combine the old fashioned oats, brown sugar, flour, baking soda, and baking powder.
Slice the cold butter into small chunks and then, using a pastry blender, cut in the cold butter to the mix. You can also use your fingers too if you don't have a pastry blender.
Just get it to a sandy texture and then sprinkle it evenly on top of the apples, pressing the topping down into an even layer on top of the apples.
Place pan into preheated oven for about 35-45 minutes, or until the topping is a nice golden brown color and the apples are bubbling.
Allow pan to cool slightly before serving and serve with a scoop of vanilla ice cream and a drizzle of caramel sauce if desired.
Let cool to room temperature and then store in an airtight container in the fridge for up to 3 days. You can reheat and serve as desired too.