Bring a large pot of salted water to a boil.
Cook the spaghetti until al dente according to package instructions.
Reserve ¼ cup of pasta water and drain the spaghetti.
Heat olive oil in a large pan over medium heat.
Sauté the chopped onion for about 3 minutes until softened.
Add minced garlic and red pepper flakes, cooking for 30 seconds until fragrant.
Stir in crushed tomatoes, salt, black pepper, and Italian seasoning.
Simmer the sauce for 8 to 10 minutes to develop flavor.
Add the cooked spaghetti and reserved pasta water to the sauce.
Toss everything together until the noodles are glossy and well coated.
Top the pasta with grated Parmesan and fresh herbs.
Serve immediately, enjoying warm.