Heat a large saucepan over medium-high heat. Add 2 tablespoons canola oil to the pan and swirl to coat. Add the onion and garlic; saute 5 minutes, stirring constantly.
Add sugar and the next 10 ingredients (through star anise); bring to a boil. Reduce heat, and simmer, partially covered, for 30 minutes or until the plums break down adn the sauce thickens, stirring occasionally. Discard the cloves and anise. Set aside 2 1/2 cups to serve with the pork.
Preheat oven to 450°.
Heat a large skillet over medium-high heat. Add 2 tablespoons oil to the pan; swirl to coat. Sprinkle pork evenly with 1/2 teaspoon salt and 1/2 teaspoon black pepper. Add the pork to the pan; saute 7 minutes, turning to brown on all sides.
Transfer the pork to a foil-lined jelly-roll pan; coat with 1/2 cup plum sauce. Roast pork at 450° for 15 minutes. Remove the pork from the oven. Turn the pork over; coat with an additional 1/2 cup plum sauce.
Roast 10 more minutes or until a thermometer inserted in the thickes portion of the pork registers 135°. Remove from the pan; let stand 10 minutes. Slice crosswise. Serve with the remaining plum sauce.