Preheat oven to 325 degrees F. Trim any excess fat from the pork loin.
Use a knife to pierce several holes in the pork. Slice the garlic into quarters and insert into the holes.
Arrange the onion slices on the bottom of a baking dish. Rub the pork with the Dijon mustard. Season the pork on all sides with salt, black pepper and paprika. Place the meat on top of the onion.
Pour the broth into the bottom of the pan. Cook in the oven for about 1 hour. Let rest for 10 minutes before slicing.