Bring a large pot of salted water to a boil. Cook penne pasta according to package instructions until al dente. Drain and set aside.
Heat olive oil in a large skillet over medium heat. Add diced onion and sauté until translucent, about 3-4 minutes.
Add minced garlic and cook for 1 minute until fragrant.
Add ground beef to the skillet. Cook, breaking it up with a spoon, until browned and cooked through, about 6-8 minutes. Season with salt and black pepper.
Pour in diced tomatoes with their juice. Stir to combine and let simmer for 5 minutes to meld flavors.
Reduce heat to low and stir in heavy cream. Allow to simmer gently for 3-4 minutes until sauce is creamy and slightly thickened.
Add cooked penne pasta to the skillet. Toss gently to coat pasta evenly with sauce and beef mixture.
Remove from heat and stir in grated parmesan cheese.
To serve, twirl pasta into neat mounds on shallow white plates. Sprinkle extra parmesan on top and garnish each plate with a fresh basil leaf.