Cook whole beets covered, in simmering water for 40-50 minutes until tender. Drain, and cool slightly, remove skin and cut into thin strips.
For dressing: combine oil, vinegar, zest, orange juice, green onion, mint and honey in screwtop jar, shake to combine. Toss half of dressing with beets, chill for 2 to 24 hours.
To serve, combine torn romaine and diced apple in a serving bowl, toss with the rest of the dressing, and top with beets. Garnish with mint.