If using a charcoal grill, preheat it to medium-hot fire. If using a gas grill, preheat it on high.
While the grill is preheating, pull back the husk and silk from the corn. Discard the silk and, using a long strip of husk, tie the husk together as shown in the picture.
Whisk together the crema, mayonnaise, garlic and lime juice.
Grill the corn directly on the grates until golden brown on all sides. This should take about 3 minutes per side.
When the corn is done, remove it from the grill and brush each ear with the crema mixture. Then sprinkle on the cheese and, if desired, also sprinkle with Tajin seasoning and juice from the lime wedges.