How to Make It
Preheat oven to 400°F. Sprinkle chicken with pepper and 3/4 teaspoon of the salt. Heat 1 tablespoon of the oil in a large cast-iron skillet over medium-high until shimmering; add chicken, and cook until browned on both sides, 3 to 4 minutes per side. Transfer to a baking sheet, and bake in preheated oven until a thermometer inserted in thickest part registers 165°F, 12 to 13 minutes.
Meanwhile, add 2 tablespoons of the oil to skillet; swirl to coat. Add green beans, corn, and scallions; cook, stirring occasionally, until beans are bright green and slightly charred, about 4 minutes. Add red bell pepper; cook, stirring occasionally, until slightly softened, about 2 minutes. Add zucchini; cook until charred and tender-crisp, about 4 more minutes. Remove from heat, and stir in tomatoes and 1/2 teaspoon of the salt.
Remove chicken from oven, and let stand 5 minutes. Meanwhile, combine vinegar, tarragon, and remaining 1/4 teaspoon salt in a small bowl. Whisk in remaining 2 tablespoons oil until combined. Slice chicken, and serve over salad. Drizzle with dressing.