Salmon & Quinoa Bowls with Green Beans Olives & Feta

1 pound salmon fillet
½ teaspoon salt, divided
¼ teaspoon ground pepper
8 ounces string beans (green, yellow, or a mix), trimmed and cut into 1-inch pieces
1 ¾ cups water
¾ cup quinoa (red, white, or tricolored), rinsed
3 tablespoons lemon juice
2 tablespoons olive oil
1 clove garlic, minced
2 teaspoons chopped fresh oregano, plus more for garnish, or 1/2 tsp. dried
1 medium tomato, seeded and chopped
¼ cup crumbled feta cheese
¼ cup pitted Kalamata olives, halved or sliced

Preheat oven to 400 degrees F. Line a large baking sheet with foil. Place salmon filet on the prepared baking sheet and sprinkle with 1/8 tsp. salt and pepper. Bake until the salmon is no longer opaque in the center and flakes easily with a fork, 20 to 25 minutes. Let rest for 5 minutes, then flake the salmon into bite-size pieces (discard the skin).
Meanwhile, bring 1 inch of water to a boil in a medium saucepan fitted with a steamer basket. Add 8 ounces beans; cover and cook until tender-crisp, about 5 minutes. Rinse the beans under cold water, drain well, and set aside. Combine 1 ¾ water, ¾ quinoa, and 1/8 tsp. salt in the saucepan; bring to a boil. Reduce heat to low, cover, and simmer until the quinoa is tender and most of the liquid has been absorbed, 15 to 20 minutes. Fluff with a fork.
Whisk 3 tablespoons lemon juice, 2 tablespoons oil, 1 clove minced garlic, 2 teaspoons chopped oregano, and the remaining 1/4 tsp. salt in a small bowl.
To serve, divide the quinoa among 4 dinner bowls. Arrange the salmon, beans, tomato, feta, and olives over the quinoa. Drizzle with the dressing and garnish with more fresh oregano, if desired.