Peel 6-8 cloves of garlic and slice in thirds. Pierce meat and insert them all around top and bottom.
Season meat with pepper and paprika. (Don't add salt because there is salt in the dried soup.).
Sear the meat by placing it fat side up on a broiler pan without the rack and broil about 5 minutes until brown. Turn and broil other side to brown.
Meanwhile, put the onion slices in the bottom of the slow cooker pot (or in the bottom of a covered roasting pan).
Combine the cranberry, soup mix and chile cause. Add water to the empty chile sauce bottle and add to the mixture. Mix all together and pour over the roast. Cover in the slow cooker and cook on low for 8-10 hours. (If you're cooking in a covered roasting pan, plan on 3-4 hours of cooking at 350 degrees in the oven. Either method works well.
When done, take the meat from the pot, separating it from the gravy. Place both in the refrigerator.
Next day, remove and discard fat from gravy. Slice the roast and place in roasting pan, covering the meat with gravy. Cover and heat in a 350 degree oven for 1 to 1 1/2 hours.
Keep warm until serving time.
Prep and cooking times do include overnight refrigeration.