Preheat your oven to 375°F (190°C).
Bring a pot of salted water to a boil and cook the whole wheat ziti according to package directions until al dente, then drain.
While the pasta cooks, heat the olive oil in a skillet over medium heat and sauté the diced onion until translucent.
Add the minced garlic and ground turkey to the skillet, breaking the meat apart with a spatula until browned and cooked through.
Stir in the baby spinach and cook until wilted, then pour in the marinara sauce, oregano, sea salt, and black pepper.
Simmer the sauce for 2-3 minutes before removing from heat.
In a small bowl, lightly stir the ricotta cheese to soften it.
Combine the cooked pasta with the turkey marinara sauce, then gently fold in dollops of the ricotta cheese so it remains slightly chunky.
Transfer the mixture to a small baking dish and sprinkle the shredded mozzarella cheese evenly over the top.
Bake for 15-20 minutes until the cheese is melted and the edges are bubbling.