Cook the penne pasta in salted water according to package instructions. Drain and set aside.
In a large skillet, heat olive oil over medium heat. Add the diced onion and sauté until softened, about 3 minutes. Add garlic and cook for another minute.
Add the Italian sausage, breaking it up with a spoon, and cook until browned and fully cooked through, about 7-8 minutes.
Stir in the crushed tomatoes, Italian seasoning, red pepper flakes, salt, and pepper. Let the sauce simmer for 10-15 minutes to thicken and allow the flavors to meld.
Add the cooked penne to the skillet and toss to coat in the sauce.
Serve hot, garnished with fresh parsley and Parmesan cheese.

Prep Time ⏲️ 10 minutes
Cook Time ⏲️ 25 minutes
Total Time ⏲️ 35 minutes
Servings 🍽️ 4
Calories 🔥 550 kcal