01 - Preheat oven to 400°F and grease a 9x13-inch baking dish with cooking spray or oil.
02 - Heat olive oil in a large skillet over medium heat. Add diced onion and cook for 2–3 minutes until softened.
03 - Add minced garlic to the skillet and cook for 30 seconds until fragrant, stirring constantly.
04 - Add ground turkey to the skillet, breaking it up with a spoon. Cook for 5–6 minutes until browned and no longer pink.
05 - Stir in red bell pepper, sweet potatoes, thyme, oregano, smoked paprika, salt, and pepper. Cook for 5 minutes, stirring occasionally.
06 - Pour in chicken broth and bring to a simmer. Cook for 8–10 minutes until sweet potatoes are just tender.
07 - Remove from heat and fold in chopped spinach until wilted.
08 - Transfer the mixture into the prepared baking dish. Sprinkle mozzarella and Parmesan evenly over the top.
09 - Bake for 18–20 minutes until the cheese is melted and golden and the casserole is bubbling.
10 - Let the casserole rest for 5 minutes before serving to allow flavors to settle.