Seared Sea Scallops and Grapefruit Salad With Mustard Vinaigrette

Ingredients

• 1 medium red onion
• 1/2 head frisée lettuce
• 4 ounces arugula
• 2 medium pink grapefruit
• 12 large sea scallops with coral
• 2 tablespoons lemon juice
• Salt and freshly ground black pepper
• 1 tablespoon butter
• 2 tablespoons dry vermouth
• 3 tablespoons olive oil
• 2 tablespoons red-wine vinegar
• 1 teaspoon whole-grain mustard
• 1 teaspoon honey