Preheat a grill or skillet over medium-high heat
Husk the corn and remove the silk
Brush the corn with melted butter or oil
Cook the corn, turning occasionally, until lightly charred and tender
Mix mayonnaise, sour cream, lime juice, chili powder, and a pinch of salt in a bowl
Spread the sauce over the cooked corn
Sprinkle with crumbled cotija cheese
Add chopped cilantro
Finish with extra chili powder and a squeeze of lime juice
Serve immediately