Place the butter and onion in a shallow casserole. Cover and cook on high for 3 minutes.
Add the ribs to the casserole dish and pour over the sauce, turning the ribs to coat. Cook on high for 4 minutes.
Spoon over the sauce again, cover and cook on low for 25 minutes, rearranging and turning the ribs every 5 minutes. Drain the sauce into a saucepan and boil on the stove top until reduced and of a syrupy consistency, about 10 minutes.
Place the ribs on a serving dish, coat with the sauce and garnish with spring onions (scallions).
Serve with rice or baked potatoes and salad.