Bring a large pot of salted water to a boil. Add the pasta and cook according to package instructions until al dente, about 8 to 10 minutes. Drain and set aside.
While the pasta cooks, heat the olive oil in a large skillet over medium-high heat.
Add the ground beef to the skillet and cook, breaking it apart with a spoon, until browned and cooked through, about 6 to 8 minutes.
Add the chopped onion to the skillet with the beef and cook until softened, about 3 to 4 minutes.
Stir in the minced garlic and cook for 1 minute until fragrant.
Pour in the marinara sauce and add the dried Italian seasoning, salt, black pepper, and crushed red pepper flakes. Stir to combine.
Reduce the heat to medium-low and simmer the sauce for 8 to 10 minutes, allowing the flavors to meld.
Add the cooked pasta to the skillet with the sauce and toss until the pasta is evenly coated.
Remove from heat and sprinkle the grated Parmesan cheese and chopped fresh parsley over the pasta. Toss gently to combine.
Serve warm.