Step 1: Prepare the corn. If using fresh corn on the cob, grill or pan-char the cobs whole until nicely browned, then slice off the kernels. Alternatively, slice kernels off cobs (or thaw frozen corn) and then char in a large, dry skillet over medium-high heat for 5-7 minutes, stirring occasionally, until kernels have golden-brown spots. Let cool slightly.
Step 2: In a large mixing bowl, combine the mayonnaise, Mexican crema (or substitute), fresh lime juice, minced garlic, chili powder, and black pepper. Whisk until smooth and well combined.
Step 3: Add the charred corn kernels, half of the crumbled Cotija cheese, chopped cilantro, and diced red onion (if using) to the dressing bowl. Gently fold all ingredients together until the corn is evenly coated.
Step 4: Taste the Elote Corn Salad and adjust seasonings as needed, adding more salt, lime juice, or chili powder to your preference.
Step 5: Transfer the Elote Corn Salad to a serving bowl. Garnish generously with the remaining crumbled Cotija cheese, a sprinkle of fresh cilantro, and an extra dusting of chili powder or Tajín. Serve immediately or chill until ready to serve.