Boil the pasta. Bring a large pot of salted water to a boil.
Cook the pasta until just al dente. Reserve 1/2 cup of pasta water, then drain.
Sauté the aromatics. In a wide skillet, warm 1 tablespoon olive oil over medium heat. Add diced onion and bell pepper.
Cook 4–5 minutes until softened. Stir in garlic and cook 30 seconds until fragrant.
Brown the turkey. Push the veggies to the edges of the pan. Add the ground turkey to the center, breaking it up with a spatula.
Season with salt, pepper, and Italian seasoning. Cook 5–7 minutes until no longer pink and lightly browned.
Build the sauce. Stir in tomato paste (if using), then add crushed tomatoes. If the sauce seems very thick, splash in broth.
Add a pinch of red pepper flakes if you like heat. Simmer on low for 10 minutes to let flavors meld.
Add greens. Fold in the chopped spinach and cook 1–2 minutes until just wilted. Taste and adjust seasoning with more salt and pepper.
If the sauce tastes flat, add a small squeeze of lemon or a pinch of sugar.
Toss with pasta. Add the drained pasta to the skillet. Toss to coat, adding reserved pasta water a splash at a time until the sauce clings silkily to the noodles.
Finish fresh. Turn off the heat. Stir in fresh basil or parsley and a drizzle of olive oil.
Top with grated Parmesan if you’d like.
Serve. Scoop into bowls and finish with extra herbs, black pepper, and a touch more cheese or lemon zest.