Preheat a grill or skillet over medium-high heat.
Remove husks and silk from fresh corn.
Brush the corn lightly with oil or melted butter.
Cook the corn, turning occasionally, until lightly charred and tender.
Mix mayonnaise and sour cream or Mexican crema in a bowl.
Spread the mixture evenly over the hot corn.
Sprinkle with crumbled cotija cheese.
Dust with chili powder or TajÃn.
Add a squeeze of fresh lime juice.
Garnish with chopped cilantro if desired.