Muffin Pan Frittatas

INGREDIENTS

• cooking spray
• 1 tablespoon olive oil
• 1 cup chopped fresh asparagus
• 1/4 cup chopped green bell pepper
• 2 tablespoons chopped red onion
• 6 eggs
• 1/2 cup milk
• 1/4 teaspoon salt
• 1/8 teaspoon ground black pepper
• 1 cup shredded Cheddar cheese