Turn crock pot to high.
Core and slice apples, chop onion and add to crock pot.
Place pork loin on top of apples and onions.
Add garlic salt and pepper on top and then top brown sugar. Pat in place.
Sprinkle crushed red peppers on top of brown sugar (gives the flavor a little kick).
Cover and cook on high for 5 hours.
After 5 hours, pop in a meat thermometer and temperature should be 160° which is perfect.
Spoon juices, apples and onions over the top then remove from crock pot.
Let rest for 15 minutes before slicing.