Preheat oven to 350 degrees F. Rinse roast and pat dry.
Place roast in a roasting pan, bone side down, fat side up.
In a bowl, mix soy sauce, brown sugar, honey and garlic. Pour the soy sauce mixture all over the roast. Scatter onions over and around the roast.
Bake, uncovered, at 350 degrees for 2 hours, or until a digital instant-read thermometer inserted into the center of the roast reads 125 degrees for medium rare, or 130 degrees for medium.
Let stand at room temperature for 15 to 20 minutes. Remove meat from bone cradle and place rib side down to carve large slices off the roast.