Have the butcher loosen the pork roast backbone, if possible, for easier carving.
Rub roast with salt and pepper.
Place bone side down in a small, shallow roasting pan.
Insert meat thermometer into thickest portion of roast; make sure bulb doesn't touch bone, fat, or pan.
Roast, uncovered, at 325 F until thermometer reads 150F, about 1 1/4 to 1 1/2 hours.
For sauce, in a medium saucepan stir together rhubarb, apple juice concentrate, honey, and nutmeg.
Bring to a boil; reduce heat, cover, and simmer for 10 minutes or until rhubarb is very tender.
Mix water and cornstarch; stir into rhubarb mixture.
Cook and stir until thickened and bubbly.
Continue cooking for 2 minutes more.
When meat thermometer registers 150F, spoon some of the sauce over the roast.
Continue roasting until thermometer reads 170F, about 30 to 45 minutes more.
Spoon on additional sauce occasionally.
Let roast stand for 15 minutes before carving.
Heat any remaining sauce and pass with roast.
MICROWAVE DIRECTIONS: Prepare and roast pork as directed.
For sauce, in a 1 1/2-quart microwave casserole cook rhubarb, apple juice concentrate, honey and nutmeg, covered at 100% power until rhubarb is very tender, about 5 to 7 minutes.
Mix water and cornstarch; stir into rhubarb mixture.
Cook, uncovered, until thickened and bubbly, about 1 to 2 minutes, stirring every 30 seconds.
Continue cooking for 1 minute more.
Spoon over roast as directed and pass remainder with roast.
