Grilled Onions and Potatoes

Ingredients

• 1 cup mayonnaise
• 1/4 cup shredded Parmesan cheese
• 3 cloves garlic, minced
• 1/4 teaspoon red pepper flakes
• 1/2 teaspoon paprika
• 1/4 teaspoon salt
• 1/4 teaspoon ground black pepper
• 3 large baking potatoes, cut into 1/4-inch slices
• 1 large sweet onion, sliced
• 4 12×12-inch squares aluminum foil
• cooking spray