– Pat the roast dry using paper towels. With a paring knife, score the skin or fat to make a diamond-shaped pattern. (Make sure not to cut the underlying meat)
– Place garlic, onion (if using), oregano, cumin, whole black pepper, orange juice and vinegar in a blender. Process until it has a very smooth texture. Set aside.
– Turn the roast on the meat side (the one that has no skin on), and with the pairing knife make some incisions about ½ inch deep, about 1 inch apart from each other.