Rinse the ribs in cold water and pat dry with paper towels.

Season on both sides with salt and pepper.

In a small bowl, combine orange juice with the spice rub to form a paste.

Rub the paste on both sides of the ribs.

Wrap the ribs in plastic wrap and refrigerate for 8 hours or overnight.

Remove from the refrigerator 30 minutes before grilling.

Set up your grill for indirect cooking, about 250 to 300 degrees F.

Place ribs, meat side up, opposite the heat source of your grill and cook for 2 hours.

Turn the ribs and grill, covered until the ribs are tender and cooked through, about 1 more hour.

Meanwhile, to prepare the plum sauce: In a medium saucepan, combine all the ingredients except the green onions.

Bring to a boil, over high heat, stirring to dissolve the sugar.

Reduce the heat to medium-low and simmer until the sauce begins to thicken and is reduced by half, about 25 minutes.

Remove from heat, add the green onion and let cool slightly.

Puree the sauce in a food processor.

Brush the ribs, on both sides, with the Asian plum sauce.

Return to indirect grilling for 15 minutes.

Remove from heat and sprinkle with sesame seeds if desired.

Let rest 10 minutes before carving.

Cut between each bone and arrange ribs on a serving platter.

Scatter green onion garnish and serve additional plum sauce on the side.

Plum sauce can be made up to 5 days in advance if tightly covered and kept in the refrigerator.