After chopping the red onion, place it in a colander and run cold water over the onion (this will remove the bite from a red onion).  Let drain.  

Heat vegetable oil in a large skillet over medium high heat. Add corn (fresh or frozen – no need to thaw), season with salt to taste and toss, then let cook, tossing only occasionally (about every 2 minutes) until corn is charred (about 6 – 10 minutes total). Remove from heat and let cool slightly.

In a serving bowl, mix together the mayonnaise, 1 Tbsp lime juice, regular chili powder, and ancho chili powder.  Add in the corn, red onion, cilantro, jalapeño, garlic, and half of the cheese.  Stir to combine.  Squeeze the remaining 1/2 Tbsp lime juice over diced avocado.  Top the salad with the avocado and remaining cheese.