1/2 cup uncooked whole-grain farro
3/4 teaspoon salt, divided
4 cups water
2 cups (2-inch) cut green beans (about 1/2 pound)
3 tablespoons extra-virgin olive oil
2 tablespoons white wine vinegar
1 tablespoon fresh lemon juice
1 teaspoon Dijon mustard
1 small garlic clove, minced
1/4 teaspoon freshly ground black pepper
1 cup grape tomatoes, halved lengthwise
1 cup very thinly sliced fennel bulb (about 1 small bulb)
1/4 cup fresh flat-leaf parsley leaves
1/4 cup oil-cured olives, pitted and coarsely chopped
5 green onions, thinly sliced
2 (4.5-ounce) jars sustainable oil-packed albacore tuna, drained (such as Wild Planet)