Heat oven to 350. Line a large cookie sheet with 2 layers of aluminum foil slightly larger than the cookie sheet.
Place quartered onion down first on foil. Rub the slab of ribs with olive oil and pack on the smoky rub on both sides. Lay them on the onions.
Mix up in a medium bowl the bbq sauce, chili sauce, and jam thoroughly. Pour over the ribs and fold foil tightly to seal. Bake at 350 for 3 hours. then remove from oven and open foil carefully (watch the steam) and lay the foil slightly back and spoon the sauce up on the ribs until covered then leave the foil open and put back into oven for 1 more hour, turn oven down to 300. These ribs should slice very easily. Spoon more on sauce as you serve.