01 - Preheat oven to 400°F. Grease a 9x13-inch baking dish with cooking spray or a light coating of oil.
02 - Heat olive oil in a large skillet over medium heat. Add diced onion and cook for 2–3 minutes until softened and translucent.
03 - Stir in minced garlic 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 completely and no longer pink.
05 - Mix in red bell pepper, diced sweet potatoes, thyme, oregano, smoked paprika, salt, and pepper. Cook for 5 minutes, stirring occasionally to coat evenly.
06 - Pour in chicken broth and bring to a gentle simmer. Cook uncovered 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 wilted from the residual heat.
08 - Spoon the turkey and vegetable 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 - Allow the casserole to rest for 5 minutes before serving to let the flavors settle and make serving easier.