01 - Preheat oven to 400°F. Lightly grease a 9x13-inch baking dish with cooking spray or olive 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 apart with a wooden spoon. Cook for 5-6 minutes until completely browned and no longer pink.
05 - Stir in red bell pepper, diced sweet potatoes, dried thyme, oregano, smoked paprika, salt, and black 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 fork-tender but not mushy.
07 - Remove skillet from heat. Fold in chopped spinach and stir until just wilted from the residual heat.
08 - Spread the turkey and vegetable mixture evenly into the prepared baking dish.
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, 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 meld and make slicing easier.