Pre-heat grill to approximate 400F degrees or grill pan to medium-high.
Using a sharp knife, slice avocados in half lengthwise and gently twist to separate. Leave the peel on but use a spoon to gently remove and discard the pit.
Remove husk and silks from corn and place tomatoes on a skewer.
Brush cut side of avocado, corn and tomatoes with olive oil. Season with Tajin and pepper.
Place avocado (cut side down), corn and tomato skewers on grates.
Avocado should take about 3 to 4 minutes to get a good sear. You can press down lightly for a few seconds to lock in some good grate marks before removing.
Let vegetables cool for 5 to 10 minutes. Shear corn off the cob and toss with grilled tomatoes and chopped fresh cilantro.
Set grilled avocados cut side up on a bed of lettuce. Pile up tomato mixture evenly among the center wells, allowing any remainder to fall over the sides onto the lettuce.
Drizzle with salad dressing and serve immediately.