1. Place farro in a large saucepan; cover with water to 2 inches above farro. Bring to a boil. Cover, reduce heat, and simmer 30 minutes. Drain and rinse with cold water; drain well.
2. Combine oil, rind, juice, vinegar, salt, and pepper in a large bowl; stir with a whisk. Add farro, tomatoes, cucumber, and cilantro; toss gently to coat. Place about 1 cup farro mixture on each of 5 plates; garnish evenly with avocado. Serve immediately.