Preheat oven to 375 degrees F. Prep a 9x13 inch baking dish.
Cook onion: heat olive oil in a large skillet over medium-high heat. Add onion and cook 3 to 4 minutes until softened.
Brown the turkey: add ground turkey, break up with a spoon. Cook 6 to 8 minutes until no pink remains. Add garlic, salt, pepper, oregano, chili powder, and paprika. Cook 1 minute.
Add vegetables: stir in diced tomatoes, cauliflower, zucchini, and spinach. Cook 3 to 4 minutes until tender but not mushy. Drain any liquid.
Transfer to dish: spread turkey mixture evenly in the baking dish.
Add cheese: sprinkle mozzarella evenly, then scatter Parmesan on top.
Bake: bake 20 to 25 minutes until cheese is melted, bubbly, and golden. Broil 1 to 2 minutes if desired for a darker top.
Finish and serve: squeeze lime juice over top, scatter cilantro or parsley. Rest 5 minutes. Serve with rice, quinoa, or a green salad.