Salmon Caesar Salad

Name: Salmon Caesar Salad
Ingredients: 1 ½ tablespoons extra-virgin olive oil; 4 (5 ounce) skinless salmon fillets (see Tip); 1 teaspoon ground pepper, divided; ⅛ teaspoon salt plus 1/2 teaspoon, divided; ½ cup buttermilk; ¼ cup nonfat plain Greek yogurt; ¼ cup grated Parmigiano-Reggiano cheese; 2 tablespoons lemon juice; 1 ½ teaspoons Worcestershire sauce; 1 teaspoon grated garlic; ½ teaspoon Dijon mustard; 5 cups chopped romaine lettuce; 3 cups chopped radicchio; 3 tablespoons thinly sliced fresh basil, plus more for garnish; 1 ½ tablespoons chopped fresh tarragon