Add the olive oil to a large oven-safe skillet over medium-high heat.
Add the onion and bell pepper, sauté for 3-5 minutes, add the garlic, saute for 1 minute.
Add the ground turkey and cook through.
Add the Italian seasoning and diced tomatoes.
Reduce the heat to low and simmer for 15 minutes.
Slice the ends off of the sweet potatoes, peel and spiralize.
Add the spiralized sweet potatoes to the skillet with the ground turkey.
Toss and cook for 3-5 minutes.
If the skillet is not oven safe, transfer the casserole to an oven-safe dish and top with the fresh mozzarella cheese. If the skillet you are using on the stovetop is oven safe, simply top with the fresh mozzarella and place in the oven.
Cover and bake for 20 minutes. Uncover and bake for 10 minutes or until the cheese is melted and bubbling.