Roasting corn in the husk in the embers of a wood fire is the best way to coax out all the natural sweetness. If also making fire-roasted potatoes, you can reserve some of the cilantro butter to season those.
Peel back the husks of the corn but do not tear off. Pull off and discard all the corn silk. In a bowl, mash the butter and cilantro together until well mixed. Rub about 1 tablespoon of cilantro butter over each ear of corn, sprinkle with salt and pepper, then pull the husks back up and around the ear. Reserve the extra butter to use on fire-roasted potatoes if desired, or use all butter on corn.
Prepare a wood fire outdoors and let cook down to embers. Place corn in embers of the fire and roast, turning with long handled tongs as husks start to blacken, until corn is cooked (about 20 minutes).
To serve, remove corn from fire with tongs. Peel back husk with hot pads and serve.