Shrimp Skewers with Charred-Tomato Vinaigrette

Name: Shrimp Skewers with Charred-Tomato Vinaigrette
Yield: 6 Servings
Ingredients: 36 large uncooked shrimp (about 2 pounds), peeled with tails left intact, deveined; 1 1/2 teaspoons coarse kosher salt; 6 metal skewers; 2 medium green onions, trimmed; 2 large plum tomatoes; 1 teaspoon plus 3/4 cup olive oil; 2 tablespoons Sherry wine vinegar; Pinch of cayenne pepper