1. Light large chimney starter filled with charcoal (6 qt, about 100 briquettes) and allow to burn until coals are fully ignited and partially covered with thin layer of ash, about 20 minutes. Arrange all coals in even layer over half of grill, leaving other half empty. Position cooking grate over coals, cover grill, and heat grate until hot, about 5 minutes; scrape grate clean with grill brush. Dip wad of paper towels in vegetable oil; holding wad with tongs, wipe cooking grate.

2. While grill is heating, combine mayonnaise, sour cream, cilantro, garlic, 1/4 teaspoon chili powder, black pepper, cayenne (if using), lime juice, and cheese in large bowl; set aside. In second large bowl, combine oil, salt, and remaining 1/2 teaspoon chili powder; add corn and toss until coated evenly.

3. Grill corn over coals, turning occasionally, until lightly charred on all sides, 7 to 12 minutes total. Remove from grill and place in bowl with mayonnaise mixture; toss to coat evenly. Serve immediately.

Serves 6