Tomatoes stuffed with Chicken Salad

INGREDIENTS

• 1 tablespoon Dijon mustard
• 1 1/2 tablespoons minced red onion
• 6 large tomatoes
• 1/2 teaspoon salt
• 1/2 cup corn, drained
• 1/4 cup plus 2 tablespoons olive oil
• 1 teaspoon ground black pepper
• 1 tablespoon chopped fresh Italian flat-leaf parsley
• 2 cups cooked and cubed chicken
• 1 tablespoon mayonnaise
• 1/4 cup fresh lemon juice
• Leaf lettuce or spinach leaves
• 1/2 cup minced red bell pepper