Husk 4 ears of corn, removing any silk. Snap off any ends that are still attached so that the cobs will fit inside a large cast-iron skillet.
Heat cast iron skillet over medium heat until very hot, about 4 minutes. You want the pan to super hot when you add the cobs so that they start to char right away. Arrange corn cobs in a single layer in skillet and cook, turning with tongs every 3-4 minutes, until charred in lots of places but not totally blackened, 15-20 minutes total.
Meanwhile, whisk ½ cup mayonnaise, ½ cup sour cream, ½ cup grated Cotija, 2 teaspoon ancho chile powder, and ½ teaspoon salt in a 9x5 loaf pan.
Finely chop 1 cup cilantro leaves (you should get about 3 tablespoons when you’re finished). Set aside 1 tablespoon cilantro for serving. Add remaining cilantro to mayonnaise mixture. Grate 1 garlic clove into mayonnaise mixture using a microplane and whisk to combine. Finely grate zest of 1 lime into mayo, then slice down the center and squeeze in the juice of half. Cut remaining 1 ½ limes into wedges; set aside for serving.
Using tongs, roll corn in mayonnaise mixture. Transfer corn to a platter, sprinkle generously with more Cotija, and dust with more ancho chile powder. Garnish with reserved 1 tablespoon. chopped cilantro. Serve reserved lime wedges alongside for squeezing over corn.