1.Boil, steam or microwave asparagus until tender; drain.
2.Combine sour cream, buttermilk and rind in a small jug; season to taste.
3.Arrange asparagus, watercress, avocado, tomato and chicken on serving plates. Drizzle with sour cream dressing; sprinkle with tarragon.
Instead of grating the lemon rind, you can use a zester to shred the rind into strips.Note