Bring a large pot of water to a boil. Cook the tortellini according to instructions on package. Drain off the tortellini and set in refrigerator to cool. Can be made ahead of time.
In a large mason jar, start by layering pesto on the bottom of the jar, then layer the following ingredients in order: cucumbers, cherry tomatoes, red onions, tortellini, and lastly mache (or romaine). Ideally the heartier and heavier ingredients are on the bottom and the more delicate lighter ingredients are on the top.
Cover and store in refrigerator for up to a week. When it’s time to eat, just shake well and serve!