Bring a large pot of water to a boil. Add tortellini and cook according to package directions, about 3 to 4 minutes, until tender. Meanwhile, place peas in colander. Drain tortellini over peas to thaw, set aside.
In large bowl, combine mayonnaise, yogurt, pesto, buttermilk, lemon juice, and Parmesan cheese, mix well. Add tortellini and peas, mix gently.
Stir in remaining ingredients and stir gently to coat. Cover and chill for 3 to 4 hours to blend flavors. Garnish with toasted pine nuts, if desired.