Preheat your grill to medium-high heat or preheat the oven to 400F (200C). Place the husked ears of corn directly on the grill grates or on a baking sheet in the oven. Grill or roast the corn for about 15-20 minutes, turning occasionally, until it's cooked and has some charred spots. The corn should be tender but not overcooked.
In a small bowl, whisk together the mayonnaise and Mexican crema (or sour cream) until well combined.
Once the corn is cooked, remove it from the grill or oven. Use a brush or a spoon to coat each ear of corn generously with the mayo-crema mixture.
Sprinkle the crumbled queso fresco or cotija cheese evenly over the mayo-crema-coated corn. Dust the corn with chili powder, cayenne pepper (if using), and a squeeze of lime juice.
Garnish the Mexican Street Corn with fresh cilantro leaves, if desired. Serve the elote hot, with extra lime wedges for squeezing over the top.
