Kale and Caramelized Onion Grilled Cheese

INGREDIENTS

• 4 medium kale leaves, stems removed
• 2 teaspoons canola oil
• 2 medium red onions, cut into 1/2-inch-thick slices
• 1/4 teaspoon freshly ground black pepper
• 1/8 teaspoon kosher salt
• 1 teaspoon red wine vinegar
• 8 (1-ounce) slices multigrain bread
• Cooking spray
• 1 ounce finely grated Parmesan cheese, divided (about 1/4 cup)
• 3.5 ounces shredded raclette cheese (about 7/8 cup)