Preheat a grill or grill pan over medium-high heat.
Grill the corn, turning occasionally, until lightly charred on the outside and tender on the inside, about 10-15 minutes.
4 ears of corn
In a small bowl, mix the mayonnaise, sour cream, Cotija cheese, chili powder, lime juice, and salt to taste.
1/4 cup mayonnaise, 1/4 cup sour cream, 1/3 cup grated cotija cheese, 3/4 teaspoon chili powder, juice of one lime, Salt
Remove the corn from the grill and allow it to cool down slightly. Brush each ear with the mayonnaise mixture. then top with cilantro, and more chili powder if desired.