Grilled Tuna With White Bean And Charred Onion Salad

Ingredients

• Tuna :
• 1 tablespoon grated lemon rind
• 2 tablespoons fresh lemon juice
• 1/2 teaspoon Dijon mustard
• 1/2 teaspoon olive oil
• 1/4 teaspoon freshly ground black pepper
• 1 garlic clove, minced
• 4 (6-ounce) tuna steaks
• Cooking spray
• Salad:
• 1 medium Vidalia or other sweet onion, cut into 1/4-inch-thick slices
• 3 tablespoons red wine vinegar
• 1 tablespoon olive oil
• 1/4 teaspoon salt
• 1/4 teaspoon freshly ground black pepper
• 1/4 teaspoon Dijon mustard
• 1 garlic clove, minced
• 1/2 cup chopped seeded peeled cucumber
• 1/4 cup chopped flat-leaf parsley
• 1 tablespoon capers
• 1 (15-ounce) can cannellini beans, rinsed and drained
• 6 cups mixed salad greens