Antioxidant-rich cacao nibs, dubbed a Mayan superfood, are roasted cacao beans that are separated from their husks and broken into tiny pieces. They are intensely aromatic with hints of chocolate, nuts and red wine and are ideal for creating bold rubs for meats such as lamb chops, chicken breasts and pork or beef tenderloin. They can be found at chocolatiers, specialty organic markets and online.
Preheat oven to 425 degrees. Line the inside of a roasting pan with aluminum foil for easy cleanup. If you don't have a roasting pan, a deep ovenproof dish will do. The dish does not have to be lined.
Using a mortar and pestle or a spice grinder, grind the cacao nibs and fennel seeds until coarse. Place in a small bowl, and add remaining ingredients through cayenne pepper. Stir well.
Using your hands, rub the tenderloin all over with 1 tablespoon canola oil. Rub all over with the cacao nib mixture, massaging it into the meat until well coated.
In a large skillet over medium-high heat, warm remaining tablespoon of canola oil. Place the tenderloin in the skillet and cook, turning it over to ensure even browning on all sides, 5 to 6 minutes. Transfer to the roasting pan and cook until a meat thermometer inserted at the thickest part of the tenderloin reads 145 degrees, about 15 minutes. Pork tenderloin cooks quickly, so it's a good idea to check it with the thermometer after 10 to 12 minutes, depending on your oven's heat.