Heat oil in a large cast iron skillet over medium heat until sizzling. Add corn and cook, stirring occasionally, until the corn is toasted and golden brown, 15 to 20 minutes. Add onion and garlic and cook for another 30 seconds. Remove from the heat and allow to cool, 10 to 15 minutes.
Mix corn mixture, jalapeno, 3 tablespoons cotija cheese, mayonnaise, lime juice, cayenne, and salt together in a mixing bowl. Adjust seasonings, adding more of your preferred flavors if desired. Top with remaining cotija cheese and cilantro.