Heat olive oil in a 12-inch skillet over medium heat. Add the diced onion and cook for about 5 minutes, stirring occasionally, until soft and translucent with just a hint of golden color around the edges.

Stir in the minced garlic and cook for 1 minute until fragrant. Add the ground beef and break it apart with a wooden spoon. Cook for 6 to 8 minutes until no pink remains and the beef picks up a light brown crust. Season generously with salt and pepper. Drain any excess fat if more than about 2 tablespoons remain in the skillet.

While the beef is in its final minutes of browning, bring a large pot of salted water to a rolling boil. Add pasta and cook until al dente, about 8 to 10 minutes. Before draining, scoop out at least half a cup of pasta water and set it aside. Drain and set aside.

Pour the broth into the skillet with the cooked beef and stir, scraping up all the browned bits from the bottom of the pan. Add the heavy cream and bring to a gentle simmer over medium heat. Let it bubble for about 3 minutes, stirring occasionally, until the sauce thickens and turns glossy.

Remove the skillet from heat completely. Stir in the freshly grated Parmesan until fully melted and smooth. Add the drained pasta and toss gently to coat every piece in the creamy sauce. If the sauce is too thick, add the reserved pasta water one tablespoon at a time. Taste and adjust seasoning as needed. Serve immediately with extra Parmesan on top.