Chop the onion.
Bring a large pot of water to a boil, then add the tortellini and cook for 3 minutes, until it floats to the top. Dump into a colander to drain, and set aside.
In a cast iron skillet, cook the ground beef, minced garlic and diced onion, and cook until no longer pink, breaking the meat apart as it cooks. Drain any grease.
Stir in the tortellini, diced tomatoes, ⅔ of the cheese and ⅔ of the bacon to the skillet. Top with remaining cheese, and sprinkle bacon over the top. Cover and cook for 5 more minutes, until the cheese is melted.