Grilled Tarragon Carrots

Name: Grilled Tarragon Carrots
Ingredients: 1/3 cup olive oil; 3 tablespoons sherry vinegar or lemon juice; 1/2 teaspoon kosher salt + more to taste; 2 tablespoons chopped fresh tarragon; 1 1/4 pounds small carrots, greens, ends, & tips removed; 1 slice from the center of a large onion about 1/2 inch thick; 1 tablespoon whole fresh tarragon leaves; salt and pepper to taste