Pull the lettuce leaves from the head, rinse gently under cold water, and lay out on clean towels to dry. Use a spoon to remove the flesh in 1 piece from each half of the avocado. Thinly slice the avocado flesh into thin wedges.
Whisk together all the dressing ingredients.
Arrange the lettuce leaves on a plate and top with the avocado wedges, scallion, and cilantro. Finish with a healthy drizzling of the dressing.