My favourite use of pork fillet/tenderloin is in a creamy peppered sauce.
1 large onion sliced
Pork fillett/tenderloin sliced
200g tub philadelphia light
400ml stock using a pork stock cube
Crushed black peppercorns
Cook the onions if frylight and remove from the pan, brown the pork fillett/tenderloin in batches, and return the onions to the pan, add the stock and philadelphia and bring to the boil, add the peppercorns to taste, and simmer until the sauce has reduced to the required consistency.
This also works well, by using mushrooms and less peppercorns, to make a creamy mushroom sauce.