Heat the olive oil in a large, heavy-bottomed pot over high heat.
Add the chopped onion and minced garlic. Cook for about 1½ minutes, stirring regularly, until fragrant and the onion begins to soften.
Add the ground beef. Cook while breaking the meat into small pieces with a wooden spoon until browned and no pink remains.
Sprinkle in the Italian herbs and cook for another 30 seconds to release their aroma.
Add the tomato paste and cook for about 1 minute, stirring it through the beef to deepen its flavor.
Pour in the crushed tomatoes and chicken broth. Add the salt, black pepper, and red pepper flakes if using. Stir well.
Add the uncooked pasta directly to the pot and stir until evenly distributed.
Bring the mixture to a gentle simmer. Cook uncovered for approximately 15 minutes, stirring every couple of minutes. Stir more frequently toward the end to prevent the pasta from sticking to the bottom.
Once the pasta is almost tender, pour the heavy cream into the One Pot Creamy Tomato Beef Pasta and stir until fully incorporated.
Simmer for another 1–2 minutes. The sauce should still look slightly loose and creamy because the pasta will continue absorbing liquid as it rests.
Remove the pot from the heat and stir thoroughly.
Spoon into bowls and finish with grated Parmesan and fresh parsley, if desired. Serve immediately while the sauce is creamy and silky.