- In a blender, purée all of the ingredients until smooth.
- In a glass dish or sealable plastic bag, coat the roast with the marinade. Cover the dish or seal the bag. Marinate for 12 to 24 hours in the refrigerator.
- With the rack in the middle position, preheat the oven to 400°F (200°C).
- Place the roast in an ovenproof skillet. Season with salt and pepper. Roast for 45 minutes or until a thermometer inserted in the centre of the roast reads 135°F (57°C). Set aside on a plate and cover with aluminum foil. Let stand for 10 minutes.
- Thinly slice and serve with pan-fried sliced plantains.