Preheat oven to 350 degrees
In a large oven safe pot, heat 1 tablespoon of oil over medium-high heat
Salt & pepper the pork loin & add to preheated pan, sear on both sides, about 3-4 minutes per side depending on how hot your pan is
When sides of pork are golden, remove from pan & set aside
Add in onion & apples, stir & cook for 1-2 minutes
Add in the apple cider & scrape bottom of the pan to loosen up all the flavors
Add the pork back in & bring to a simmer
Cover & place in oven
Cook for about 15-20 minutes per pound (the searing started the cooking process already- if you do not sear, cook for 20-25 minutes per pound)
When done, remove pork to a plate & cover with foil. Let rest for a few minutes
To make the gravy, place the pan on medium-high heat & bring to a boil
Mix the corn starch & water or cider together & whisk into the gravy
Stir until thickened
Slice up the pork & serve with the gravy