Crisp Salmon with Braised Red Cabbage and Mustard Sauce

INGREDIENTS

• 2 teaspoons olive oil
• 1/3 cup finely chopped onion
• 1/2 pound red cabbage (about 1/2 small head), thinly sliced (about 4 cups)
• 3/4 teaspoon coarse salt
• 3 tablespoons balsamic vinegar
• Vegetable-oil cooking spray
• 4 salmon fillets, with skin (5 ounces each)
• Freshly ground black pepper
• 2 teaspoons Dijon mustard