Arrange the lettuce on a plate, add the cherry tomatoes, red onion and sliced hearts of palm. Toss the lobster meat with a little of the avocado dressing; place the lobster salad in the middle of the plate, drizzle with the remaining Avocado-Buttermilk dressing.
Combine all the ingredients in a blender and blend on high speed until smooth, scraping down the sides as needed. Adjust the seasoning, to taste.
Transfer to a bowl, cover, and refrigerate until ready to use. (The dressing can be made up to 4 hours in advance.)