For the guacamole: Combine the cilantro, tomatillos, garlic, avocado, jalapeno, onion, lime juice, cumin and salt in a food processor or blender and pulse until combined. Set aside 1/2 cup of the guacamole for the creamy tomatillo dressing, and use remaining guacamole for another recipe.
For the charred corn salad: Preheat a grill pan over high heat. Brush or rub each ear of corn with the canola oil and sprinkle with salt and black pepper. Grill the corn until it gets a nice char, 2 to 3 minutes per side. Set aside until cool enough to handle, about 5 minutes. Stand each ear stalk-end down, in a wide, shallow bowl and slice the kernels off using your knife.
Combine the corn kernels, lime juice, avocado, Fresno chiles and red onions in a large bowl.
For the creamy tomatillo dressing: Mix together the mayonnaise, 1/2 cup tomatillo guacamole, hot sauce, chili powder and cumin. Add to the corn salad and toss to combine.
Fold in the cilantro and crumbled cotija and season with salt.
Serving suggestion: Portion the salad into small cups, squeeze additional lime over the top, and serve with a spoon.