In a medium bowl, whisk together the mayonnaise, yogurt, lemon juice, lemon zest, salt, pepper, sugar and tarragon until combined. Set aside.
Place the corn directly on the grill rack and cook until charred on all sides, approximately 1-2 minutes on each side. Transfer to a plate and allow to cool.
In a large bowl, add the pasta, lobster, tomatoes and scallions. Cut the corn off the cob and add to the bowl.
Pour the dressing over the salad and toss to combine. Cover and chill for up to two hours. Serve with chopped tarragon and lemon wedges, if desired
Notes
Lobster Pasta Salad can be made up to 24 hours in advance. Cover and refrigerate until ready to serve.