Toss the sweet potatoes with the avocado oil, salt and pepper on a lined baking sheet. Roast the potatoes for 40 minutes, stirring occasionally. When finished, allow to cool slightly.
While the potatoes are roasting, combine the pearl barley, lentils, and water (or vegetable stock) in a small pot. Bring to a boil and reduce to a simmer for approximately 40 minutes or until tender and all the liquid has been absorbed.
When the lentils and barley have finished cooking, add the spinach to the pot. Cover and allow to wilt slightly, about five minutes.
In a large bowl, combine the sweet potatoes, lentil mixture, and tuna. Stir to combine and top with hard boiled eggs and herb dressing.
For the Dressing
Combine the dressing incredients in the bowl of a small food processor. Process to combine.
1/4 cup fresh dill and 1/4 cup fresh chives can be substituted for the dried herbs in the dressing.