Bring a large pot of salted water to a boil.
Cook the penne according to package directions until al dente.
Reserve 1/2 cup pasta water and drain the pasta.
Heat olive oil in a large skillet over medium heat.
Add the garlic and red pepper flakes.
Cook for about 1 minute until fragrant.
Stir in the crushed tomatoes.
Add salt, black pepper, and Italian seasoning.
Simmer for 15 to 20 minutes, stirring occasionally.
Add a splash of reserved pasta water if the sauce becomes too thick.
Add the cooked pasta to the skillet.
Toss until the pasta is evenly coated.
Stir in the parsley.
Top with Parmesan cheese if desired and serve immediately.