In a large bowl, combine jam, vinegar, tomato paste, and 1 Tbsp oil. Season with salt and pepper and set aside.
Assemble 4 long skewers, alternating 4 pork cubes with 2 onion wedges and 2 apple wedges on each (begin with pork, end with apple).
Arrange skewers into a non-reactive dish; pour marinade over.
To Freeze: Freeze in freezer safe container.
To Reheat: Grill until done.