Mix together the mayonnaise, tarragon, vinegar, garlic powder, salt, pepper and lemon juice in a large bowl. Add the tomatoes, buns, bacon, scallions and celery to the dressing and toss to coat. Fold in the lobster and avocado. Serve immediately!
This is a great use for leftover buttered hot dog (or hamburger) buns from a cookout. If you don't have any leftovers, spread 3 tablespoons softened unsalted butter on the buns and toast in a 375 degree F oven for 10 minutes.