Bring a large pot of salted water to a boil. Add the penne pasta and cook according to package instructions until al dente, about 10-12 minutes. Drain and set aside.
While the pasta cooks, heat olive oil in a large skillet over medium heat.
Add the diced onion to the skillet and sauté for 3-4 minutes until softened.
Add the minced garlic and cook for 1 minute until fragrant.
Add the ground turkey to the skillet. Cook, breaking it up with a spoon, until browned and cooked through, about 6-8 minutes.
Stir in the diced tomatoes with their juice, tomato sauce, dried oregano, dried basil, salt, black pepper, and crushed red pepper flakes.
Bring the sauce to a simmer and cook for 8-10 minutes, stirring occasionally, until slightly thickened.
Add the cooked pasta to the skillet with the turkey sauce and toss to combine evenly.
Remove from heat and stir in the grated Parmesan cheese.
Garnish with chopped fresh parsley before serving.