In a large, heavy saucepan over medium-high heat, add the farro, 2 teaspoons salt, and water (or stock, if using). Bring to a simmer, cover and cook, stirring occasionally, until the farro is tender, 35 to 45 minutes. Check a few times while it is cooking, you want it to be al dente. Remove from the heat, drain any excess water, and set aside to cool.
While the grains are simmering make the dressing. Whisk together the orange zest and juice, shallots, white balsamic vinegar, and olive oil. Add salt and pepper, to taste, and set aside.
Just before serving, in a large bowl, toss the farro with 3 tablespoons dressing and transfer to a large serving bowl. In the same large bowl, combine the salad greens with the almonds, prunes, cherries, and onions and gently toss with 3 tablespoons remaining dressing, adding more dressing as needed. Plate the greens mixture on top of the faro and serve.