Start by preparing the dressing. Add all of the ingredients to a small food processor or to a small bowl and use an immersion blender. Process until smooth and refrigerate.
Cut the avocado in half and remove the pit. Peel away the outer skin of the avocado and place the flesh cut-side down on a cutting board. Dice the avocado and place into a small bowl. Set aside.
Pre-heat your grill or griddle pan to medium-high. Prep the corn and romaine for grilling by brushing with olive oil and sprinkling with coarse ground salt and freshly ground pepper. Place the corn on the grill and cook on all sides until a few kernels start to char, about 7-10 minutes. Once the corn is cool enough to handle, cut the kernels off the cob. Remove from the grill and set aside. Place the romaine on the grill cut-side down and cook for 1-2 minutes.
Serve immediately by placing the grilled romaine on a plate, cut side up, topped with avocado, corn, and cilantro. Serve with dressing on the side.