01 - Preheat oven to 400°F. Grease a 9x13-inch baking dish with cooking spray or a light coating of oil.
02 - In a large skillet, heat olive oil over medium heat. Add diced onion and cook for 2–3 minutes until softened and translucent.
03 - Add minced garlic to the skillet and cook for 30 seconds until fragrant, being careful not to burn it.
04 - Add ground turkey to the skillet, breaking it up with a wooden spoon. Cook for 5–6 minutes until browned and no longer pink.
05 - Stir in red bell pepper, diced sweet potatoes, dried thyme, oregano, smoked paprika, salt, and pepper. Cook for 5 minutes, stirring occasionally to combine flavors.
06 - Pour in chicken broth and bring to a gentle simmer. Cook for 8–10 minutes until sweet potatoes are just tender when pierced with a fork.
07 - Remove skillet from heat. Fold in chopped spinach and stir until just wilted from the residual heat.
08 - Transfer the entire mixture into the prepared baking dish, spreading it evenly.
09 - Sprinkle shredded mozzarella and grated Parmesan cheese evenly over the top of the casserole.
10 - Bake for 18–20 minutes until the cheese is melted and golden brown, and the casserole is bubbling around the edges.
11 - Let the casserole rest for 5 minutes before serving to allow the flavors to settle and make slicing easier.