Cast Iron Turkey Burgers

Ingredients

• 1 pound ground turkey
• 1⁄4 cup chopped yellow onion
• 1 tablespoon olive oil
• 1 teaspoon sea salt
• 1⁄4 teaspoon ground black pepper
• 4 romaine lettuce leaves
• 1 avocado, sliced
• 4 burger buns (sprouted grain or gluten free)