Step 1: Preheat your oven to 400°F (200°C) and lightly grease a 9×13 inch baking dish.
Step 2: In a large skillet over medium heat, add 1 tablespoon of olive oil and sauté the diced onion and bell pepper for 5 minutes until soft.
Step 3: Add the ground turkey to the skillet. Cook, breaking it up with a spoon, until fully browned and no longer pink. Stir in the minced garlic for the last minute.
Step 4: In a large bowl, toss the cubed sweet potatoes with the remaining olive oil, smoked paprika, cumin, garlic powder, salt, and pepper.
Step 5: Mix the cooked turkey and vegetable mixture into the bowl with the sweet potatoes. Transfer the entire ground turkey sweet potato bake mixture into the prepared baking dish.
Step 6: Cover the dish tightly with aluminum foil and bake for 20 minutes.
Step 7: Remove from the oven, take off the foil, and stir in the fresh spinach. Top with shredded mozzarella if using.
Step 8: Bake uncovered for an additional 15-20 minutes until the sweet potatoes are tender and slightly browned. Let the ground turkey sweet potato bake rest for 5 minutes before serving.