Lobster Salad with Greens and Citrus Vinaigrette

Name: Lobster Salad with Greens and Citrus Vinaigrette
Ingredients: 2 whole lobsters (1 ¾ pounds each); 2 tablespoons extra-virgin olive oil; 1 ½ teaspoons finely grated orange zest, plus 1 tablespoon fresh orange juice; 1 ½ teaspoons finely grated lemon zest, plus 2 tablespoons fresh lemon juice; 1 teaspoon Dijon mustard; ¼ teaspoon finely grated shallot; Coarse salt; 12 cups mixed greens such as Bibb lettuce, mache, and arugula (10 ounces); 1 large yellow tomato, halved and thinly sliced; 2 teaspoons finely chopped fresh tarragon, plus more for garnish