Bring a large pot of water to a rolling boil. Add 1/2 teaspoon salt, then pasta. Cook until "al dente," according to package directions. Drain and set aside.
In a large skillet over medium-high heat, add ground turkey, breaking up with a fork as it cooks. Continue cooking until it loses its pink color, drain off excess fat. Add marinara and spaghetti, toss to combine.
Preheat the oven to 375°F
Combine in a mixing bowl baby spinach, 1/2 teaspoon salt, pepper, oregano, basil, and all cheese.
In a 9 x 13-inch casserole dish, layer 1/2 spaghetti and meat sauce mixture, then 1/2 of spinach cheese mixture. Repeat the layering.
Cover with foil and bake 25 minutes.
Remove foil and bake an additional 5 minutes, or until the cheese is hot and bubbly. Garnish with fresh basil leaves if desired.