Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the ground turkey, diced onion, minced garlic, shredded carrots, and chopped spinach.
Add the dried thyme, salt, black pepper, breadcrumbs, and eggs to the mixture. Mix everything well until fully combined.
Lightly grease the baking dish with cooking spray or oil. Transfer the turkey mixture into the baking dish and shape it into an even cake.
Spread the marinara sauce on top of the turkey cake, ensuring it's evenly covered.
Sprinkle the grated parmesan cheese over the sauce.
Top with shredded mozzarella cheese.
Place the baking dish in the preheated oven and bake for 60 minutes, or until the internal temperature reaches 165°F (75°C) and the top is golden brown.
Remove from the oven and let it sit for 10 minutes before slicing and serving.