Wash and place the pork on a baking pan. Season with salt and pepper. Put cayenne pepper and oregano on the side of the meat that touches the pan. Throw onion circlets on top.
Preheat the oven at 200C and put the pork inside. Brown on both sides, for 10 minutes each, turning the meat once.
Wash celery, leek, carrot, onion, chop them well and add to the pan. Cover the meat with a baking sheet.
Roast for 1 hour, turn the pork over and roast for 1 more hour.
Prepare the sauce by mixing the wine with the flour and 2 cups of the pork's juices. Pour over the meat and serve.
