Heat the oil in a large pan; add bacon and sauté 3-4 minutes until crispy. Remove bacon with a slotted spoon and set aside. Add the onion and 2 sprigs of thyme to the pan, season with salt and pepper and cook on low heat for 5 minutes. Sprinkle with sugar and splash with the vinegar.
Cook 5 minutes more stirring from time to time until, onion is brown and caramelized. Add bacon back to the pan.
In the meantime, cook the Tortelloni in a large saucepan of salted boiling water according to package instructions and drain reserving ¼ cup of cooking water. Add the Tortelloni to the pan with reserved liquid and toss to combine.
Divide between plates, drizzle with little oil, top with thyme leaves and black pepper to taste.