Heat oil in a large skillet over medium heat. Saute onion and bacon until onion is translucent and bacon is brown; remove from skillet and drain on paper towelling. Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain. Return onion/bacon mixture to skillet and add cooked tortellini. Toss with 2 tablespoons olive oil and heat through. Place in serving dish or bowl, sprinkle with vinegar and cheese and serve immediately.