GRILL DIRECTIONS: Heat grill. In small bowl, combine 1 tablespoon cherry juice blend and cornstarch; blend well. Set aside.
In medium saucepan, combine rhubarb and 1 cup cherry juice blend. Bring to a boil. Reduce heat; cover and simmer about 8 minutes or until rhubarb is very tender.
Strain rhubarb; discard pulp, reserving juice. Return juice to saucepan; add cherries. Bring to a boil. Reduce heat; cover and simmer 10 minutes or until slightly thickened. Stir in cornstarch mixture. Bring to a boil. Cook 1 minute or until thickened and bubbly, stirring constantly.
Meanwhile, sprinkle pork tenderloins with salt and pepper. Place pork on gas grill over medium heat or on charcoal grill 4 to 6 inches from medium coals; cover grill. Cook 20 to 25 minutes or until pork is no longer pink in center, turning occasionally and brushing with sauce during last 10 minutes of cooking time. (Pork is done when thermometer inserted in center of tenderloin registers 150 to 160°F.)
To serve, bring remaining sauce to a boil. Serve sauce over pork.