Heat a cast iron grill pan over medium-high heat.* Grease as needed with butter.
Place the ears of corn on the pan to cook. Turn the ears every 2–3 minutes until they are tender and charred in places all the way around, about 15 minutes total.
Meanwhile, stir together the mayonnaise, sour cream, chile powder, garlic, and cilantro.
When the ears are smoky and cooked through, remove them from the grill pan. Immediately slather with the cheesy sauce.
Sprinkle with a little extra cheese and cilantro, and drizzle with lime juice. Serve hot.
Notes
*Of course, the corn may be grilled as well, ideally over charcoal flames!