In a 5 quart pot, cook pasta according to package instructions; drain, and rinse with cold water until cool to the touch; set aside.
In a mixing bowl, combine yogurt, pesto, mayonnaise, olive oil, salt, and pepper; set aside.
When ready to combine, gently fold in the dressing to coat tortellini; then fold in the tomatoes; cover and refrigerate until ready to serve. Garnish with parmesan cheese and parsley.
Notes
Serving suggestion: When you make the dressing, set aside 1/3 cup. You can use this to freshen up the salad because it will have absorbed the dressing.