Cook Tortellini for 6 minutes, drain and place in an ice water bath.
When cool, drain again and place in a large bowl. Toss well with olive oil to prevent Tortellini from sticking together.
Cook bacon until crispy and lay on paper towels to drain. Crumble into small pieces (remove fat if desired).
Add bacon, tomatoes and onion to Tortellini and toss.
For the dressing: In a small bowl, whisk mayonnaise, vinegar, basil (reserving some for garnish), salt and pepper. Add dressing to Tortellini and toss again.
Garnish with remaining basil. Option: Add avocado.