Make a green salad base inside a container with the chopped Romaine lettuce. Top with grape tomatoes, thinly sliced red onions (if using) and diced avocado. If packing this the night before, dice up the avocado in the morning.
Fill a small lidded container with the dressing and wait to drizzle it over the salad at lunch. This prevents the lettuce from getting soggy.
Refrigerate the salad or pack it with an ice pack inside a lunch bag.
Notes
Nutritional information is calculated without dressing.