Bring a large pot of salted water to a boil. Add penne pasta and cook according to package instructions until al dente. Drain and set aside.
While pasta cooks, heat olive oil in a large skillet over medium heat. Add diced onion and minced garlic; sauté until softened and fragrant, about 3-4 minutes.
Add ground beef to the skillet. Cook, breaking it up with a spoon, until browned and cooked through, about 6-8 minutes.
Stir in diced tomatoes, dried oregano, salt, and black pepper. Simmer for 5 minutes to meld flavors.
Reduce heat to low and stir in heavy cream. Add cooked penne pasta to the skillet and toss to coat evenly with the creamy tomato sauce.
Remove from heat and stir in grated parmesan cheese and fresh basil leaves.
Plate the pasta by twirling it into a neat mound in the center of shallow white plates. Top each serving with extra parmesan and basil leaves.