Make the cilantro lime crema. If making in a blender, place ⅔ cup sour cream, ½ cup loosely packed cilantro leaves, 1 finely chopped garlic clove, lime zest and juice, and a pinch of Kosher salt in the bowl of a blender, then process until very smooth. Otherwise, whisk together all ingredients until smooth. Cover and refrigerate until needed.
Char the corn in the husks. Preheat a grill over medium-high heat until it reaches 475°F (245°C). When very hot, grease the grill grates with grill spray, then carefully add the corn. Cook, turning, occasionally, until charred on all sides, about 4-6 minutes.
Remove the husks, then return to the grill. Gently pull down the husk on each ear of corn. You can either remove them completely, or simply fold them over. Brush the corn with a little melted butter, then return to the grill. Cook, turning every minute or so, until the corn is blistered and charred a little, another 4-6 minutes. Transfer to a serving tray.
Garnish, then serve. Drizzle the cilantro crema on top of the corn, then sprinkle with crumbled cotija, as much Cayenne pepper as you like, and lots of fresh cilantro. Serve immediately with lime wedges on the side.
Note: If you don’t want to use Cayenne pepper, you can substitute with sweet paprika or smoked paprika.