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