Place beets in a large saucepan; cover with water. Bring to a boil. Reduce heat; cover and cook for 25-30 minutes or until tender. Drain and cool slightly. Peel and slice; place in a serving bowl and keep warm., In a small saucepan, combine the sugar, cornstarch and pepper; stir in orange juice until smooth. Bring to a boil; cook and stir for 2 minutes or until thickened. Remove from the heat; stir in orange slices if desired and zest. Pour over beets.