While the pork is resting, pour away the fat from the roasting tray (it can be used for roasting potatoes). Place the tray on top of the stove over a medium heat, add the flour and stir into the onion.
Whisk in the cider and stock a little at a time. Bring the gravy to a simmer and cook for a few minutes, seasoning with salt and pepper. The gravy can be served like