Bring a large pot of water to a boil and add 1 tablespoon of salt. Cook the penne according to package directions until al dente, about 10-12 minutes. Before draining, scoop out 1/2 cup of the starchy pasta water and set aside. Then drain the pasta.

While the pasta cooks, heat 2 tablespoons of olive oil in a large skillet over medium heat. Add the chopped onion and cook for 3-4 minutes, stirring occasionally, until translucent and soft. Stir in the minced garlic and cook for another 30-60 seconds until fragrant but not browned.

Add the ground beef to the skillet, breaking it up with a wooden spoon or spatula as it cooks. Continue cooking for 5-7 minutes until completely browned with no pink remaining. If excess fat pools in the pan, carefully drain it off.

Stir in the diced tomatoes with their juices, beef broth, and Italian seasoning. Bring to a gentle simmer and cook for 3-4 minutes to blend flavors. The sauce should reduce slightly and lightly coat the back of a spoon.

Remove the skillet from heat and let cool for about 1 minute. This prevents the Greek yogurt from separating. Stir in the Greek yogurt and Parmesan cheese until smooth and creamy. Taste and season with salt and pepper as needed.

Add the cooked pasta to the skillet and toss until well coated with the creamy beef sauce. If the sauce seems too thick, add reserved pasta water a splash at a time until desired consistency is reached. Garnish with freshly chopped basil or parsley before serving.